diff --git a/cpp/ql/lib/semmle/code/cpp/dataflow/internal/FlowSummaryImpl.qll b/cpp/ql/lib/semmle/code/cpp/dataflow/internal/FlowSummaryImpl.qll
index d89ab06ed829..a1d9dd86c400 100644
--- a/cpp/ql/lib/semmle/code/cpp/dataflow/internal/FlowSummaryImpl.qll
+++ b/cpp/ql/lib/semmle/code/cpp/dataflow/internal/FlowSummaryImpl.qll
@@ -148,6 +148,19 @@ module SourceSinkInterpretationInput implements
     )
   }
 
+  predicate barrierElement(
+    Element n, string output, string kind, Public::Provenance provenance, string model
+  ) {
+    none()
+  }
+
+  predicate barrierGuardElement(
+    Element n, string input, Public::AcceptingValue acceptingvalue, string kind,
+    Public::Provenance provenance, string model
+  ) {
+    none()
+  }
+
   private newtype TInterpretNode =
     TElement_(Element n) or
     TNode_(Node n)
diff --git a/csharp/ql/lib/semmle/code/csharp/dataflow/internal/FlowSummaryImpl.qll b/csharp/ql/lib/semmle/code/csharp/dataflow/internal/FlowSummaryImpl.qll
index 3ee16f21489c..842c28ac75b0 100644
--- a/csharp/ql/lib/semmle/code/csharp/dataflow/internal/FlowSummaryImpl.qll
+++ b/csharp/ql/lib/semmle/code/csharp/dataflow/internal/FlowSummaryImpl.qll
@@ -235,6 +235,19 @@ module SourceSinkInterpretationInput implements
     )
   }
 
+  predicate barrierElement(
+    Element n, string output, string kind, Public::Provenance provenance, string model
+  ) {
+    none()
+  }
+
+  predicate barrierGuardElement(
+    Element n, string input, Public::AcceptingValue acceptingvalue, string kind,
+    Public::Provenance provenance, string model
+  ) {
+    none()
+  }
+
   class SourceOrSinkElement = Element;
 
   private newtype TInterpretNode =
diff --git a/go/ql/lib/semmle/go/dataflow/internal/FlowSummaryImpl.qll b/go/ql/lib/semmle/go/dataflow/internal/FlowSummaryImpl.qll
index f12c9e6eeb1b..41ded04634be 100644
--- a/go/ql/lib/semmle/go/dataflow/internal/FlowSummaryImpl.qll
+++ b/go/ql/lib/semmle/go/dataflow/internal/FlowSummaryImpl.qll
@@ -163,6 +163,19 @@ module SourceSinkInterpretationInput implements
     )
   }
 
+  predicate barrierElement(
+    Element n, string output, string kind, Public::Provenance provenance, string model
+  ) {
+    none()
+  }
+
+  predicate barrierGuardElement(
+    Element n, string input, Public::AcceptingValue acceptingvalue, string kind,
+    Public::Provenance provenance, string model
+  ) {
+    none()
+  }
+
   // Note that due to embedding, which is currently implemented via some
   // Methods having multiple qualified names, a given Method is liable to have
   // more than one SourceOrSinkElement, one for each of the names it claims.
diff --git a/java/ql/lib/ext/empty.model.yml b/java/ql/lib/ext/empty.model.yml
index 43028e7cc14e..a0ea3cf753ba 100644
--- a/java/ql/lib/ext/empty.model.yml
+++ b/java/ql/lib/ext/empty.model.yml
@@ -13,6 +13,14 @@ extensions:
       pack: codeql/java-all
       extensible: summaryModel
     data: []
+  - addsTo:
+      pack: codeql/java-all
+      extensible: barrierModel
+    data: []
+  - addsTo:
+      pack: codeql/java-all
+      extensible: barrierGuardModel
+    data: []
   - addsTo:
       pack: codeql/java-all
       extensible: neutralModel
diff --git a/java/ql/lib/ext/hudson.model.yml b/java/ql/lib/ext/hudson.model.yml
index eda30b6a0ff7..0dfff091fcd4 100644
--- a/java/ql/lib/ext/hudson.model.yml
+++ b/java/ql/lib/ext/hudson.model.yml
@@ -50,6 +50,12 @@ extensions:
       - ["hudson", "FilePath", False, "readToString", "", "", "ReturnValue", "file", "manual"]
       - ["hudson", "Plugin", True, "configure", "", "", "Parameter", "remote", "manual"]
       - ["hudson", "Plugin", True, "newInstance", "", "", "Parameter", "remote", "manual"]
+  - addsTo:
+      pack: codeql/java-all
+      extensible: barrierModel
+    data:
+      - ["hudson", "Util", True, "escape", "(String)", "", "ReturnValue", "html-injection", "manual"]
+        # Not including xmlEscape because it only accounts for >, <, and &. It does not account for ", or ', which makes it an incomplete XSS sanitizer.
   - addsTo:
       pack: codeql/java-all
       extensible: summaryModel
diff --git a/java/ql/lib/ext/java.io.model.yml b/java/ql/lib/ext/java.io.model.yml
index 3582e2b78ac6..07e39c9e12f7 100644
--- a/java/ql/lib/ext/java.io.model.yml
+++ b/java/ql/lib/ext/java.io.model.yml
@@ -162,3 +162,8 @@ extensions:
       extensible: sourceModel
     data:
       - ["java.io", "FileInputStream", True, "FileInputStream", "", "", "Argument[this]", "file", "manual"]
+  - addsTo:
+      pack: codeql/java-all
+      extensible: barrierModel
+    data:
+      - ["java.io", "File", True, "getName", "()", "", "ReturnValue", "path-injection", "manual"]
diff --git a/java/ql/lib/ext/java.net.model.yml b/java/ql/lib/ext/java.net.model.yml
index 084fce7bbc4b..e69db468a4a4 100644
--- a/java/ql/lib/ext/java.net.model.yml
+++ b/java/ql/lib/ext/java.net.model.yml
@@ -34,6 +34,11 @@ extensions:
       - ["java.net", "URLClassLoader", False, "URLClassLoader", "(URL[],ClassLoader)", "", "Argument[0]", "request-forgery", "manual"]
       - ["java.net", "URLClassLoader", False, "URLClassLoader", "(URL[])", "", "Argument[0]", "request-forgery", "manual"]
       - ["java.net", "PasswordAuthentication", False, "PasswordAuthentication", "(String,char[])", "", "Argument[0]", "credentials-username", "hq-generated"]
+  - addsTo:
+      pack: codeql/java-all
+      extensible: barrierGuardModel
+    data:
+      - ["java.net", "URI", True, "isAbsolute", "()", "", "Argument[this]", "false", "request-forgery", "manual"]
   - addsTo:
       pack: codeql/java-all
       extensible: summaryModel
diff --git a/java/ql/lib/ext/java.util.regex.model.yml b/java/ql/lib/ext/java.util.regex.model.yml
index 4f0776e59bd2..20269a271b55 100644
--- a/java/ql/lib/ext/java.util.regex.model.yml
+++ b/java/ql/lib/ext/java.util.regex.model.yml
@@ -12,6 +12,11 @@ extensions:
       - ["java.util.regex", "Pattern", False, "split", "(CharSequence)", "", "Argument[this]", "regex-use[0]", "manual"]
       - ["java.util.regex", "Pattern", False, "split", "(CharSequence,int)", "", "Argument[this]", "regex-use[0]", "manual"]
       - ["java.util.regex", "Pattern", False, "splitAsStream", "(CharSequence)", "", "Argument[this]", "regex-use[0]", "manual"]
+  - addsTo:
+      pack: codeql/java-all
+      extensible: barrierModel
+    data:
+      - ["java.util.regex", "Pattern", False, "quote", "(String)", "", "ReturnValue", "regex-use", "manual"]
   - addsTo:
       pack: codeql/java-all
       extensible: summaryModel
diff --git a/java/ql/lib/ext/org.owasp.esapi.model.yml b/java/ql/lib/ext/org.owasp.esapi.model.yml
index 30578debe580..70890d7e03b3 100644
--- a/java/ql/lib/ext/org.owasp.esapi.model.yml
+++ b/java/ql/lib/ext/org.owasp.esapi.model.yml
@@ -1,6 +1,42 @@
 extensions:
+  - addsTo:
+      pack: codeql/java-all
+      extensible: barrierGuardModel
+    data:
+      - ["org.owasp.esapi", "Validator", true, "isValidCreditCard", "", "", "Argument[1]", "true", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "isValidDate", "", "", "Argument[1]", "true", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "isValidDirectoryPath", "", "", "Argument[1]", "true", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "isValidDouble", "", "", "Argument[1]", "true", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "isValidFileContent", "", "", "Argument[1]", "true", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "isValidFileName", "", "", "Argument[1]", "true", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "isValidInput", "", "", "Argument[1]", "true", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "isValidInteger", "", "", "Argument[1]", "true", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "isValidListItem", "", "", "Argument[1]", "true", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "isValidNumber", "", "", "Argument[1]", "true", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "isValidPrintable", "", "", "Argument[1]", "true", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "isValidRedirectLocation", "", "", "Argument[1]", "true", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "isValidSafeHTML", "", "", "Argument[1]", "true", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "isValidURI", "", "", "Argument[1]", "true", "trust-boundary-violation", "manual"]
+  - addsTo:
+      pack: codeql/java-all
+      extensible: barrierModel
+    data:
+      - ["org.owasp.esapi", "Validator", true, "getValidCreditCard", "", "", "ReturnValue", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "getValidDate", "", "", "ReturnValue", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "getValidDirectoryPath", "", "", "ReturnValue", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "getValidDouble", "", "", "ReturnValue", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "getValidFileContent", "", "", "ReturnValue", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "getValidFileName", "", "", "ReturnValue", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "getValidInput", "", "", "ReturnValue", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "getValidInteger", "", "", "ReturnValue", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "getValidListItem", "", "", "ReturnValue", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "getValidNumber", "", "", "ReturnValue", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "getValidPrintable", "", "", "ReturnValue", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "getValidRedirectLocation", "", "", "ReturnValue", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "getValidSafeHTML", "", "", "ReturnValue", "trust-boundary-violation", "manual"]
+      - ["org.owasp.esapi", "Validator", true, "getValidURI", "", "", "ReturnValue", "trust-boundary-violation", "manual"]
   - addsTo:
       pack: codeql/java-all
       extensible: summaryModel
     data:
-      - ["org.owasp.esapi", "Encoder", true, "encodeForHTML", "(String)", "", "Argument[0]", "ReturnValue", "taint", "manual"]
\ No newline at end of file
+      - ["org.owasp.esapi", "Encoder", true, "encodeForHTML", "(String)", "", "Argument[0]", "ReturnValue", "taint", "manual"]
diff --git a/java/ql/lib/semmle/code/java/dataflow/ExternalFlow.qll b/java/ql/lib/semmle/code/java/dataflow/ExternalFlow.qll
index d1849df0f3ec..e612239a76ec 100644
--- a/java/ql/lib/semmle/code/java/dataflow/ExternalFlow.qll
+++ b/java/ql/lib/semmle/code/java/dataflow/ExternalFlow.qll
@@ -91,6 +91,7 @@ module;
 
 import java
 private import semmle.code.java.dataflow.DataFlow::DataFlow
+private import semmle.code.java.controlflow.Guards
 private import FlowSummary as FlowSummary
 private import internal.DataFlowPrivate
 private import internal.FlowSummaryImpl
@@ -174,6 +175,24 @@ predicate sinkModel(
   )
 }
 
+/** Holds if a barrier model exists for the given parameters. */
+predicate barrierModel(
+  string package, string type, boolean subtypes, string name, string signature, string ext,
+  string output, string kind, string provenance, QlBuiltins::ExtensionId madId
+) {
+  Extensions::barrierModel(package, type, subtypes, name, signature, ext, output, kind, provenance,
+    madId)
+}
+
+/** Holds if a barrier guard model exists for the given parameters. */
+predicate barrierGuardModel(
+  string package, string type, boolean subtypes, string name, string signature, string ext,
+  string input, string acceptingvalue, string kind, string provenance, QlBuiltins::ExtensionId madId
+) {
+  Extensions::barrierGuardModel(package, type, subtypes, name, signature, ext, input,
+    acceptingvalue, kind, provenance, madId)
+}
+
 /** Holds if a summary model exists for the given parameters. */
 predicate summaryModel(
   string package, string type, boolean subtypes, string name, string signature, string ext,
@@ -234,6 +253,7 @@ predicate interpretModelForTest(QlBuiltins::ExtensionId madId, string model) {
       "Summary: " + package + "; " + type + "; " + subtypes + "; " + name + "; " + signature + "; " +
         ext + "; " + input + "; " + output + "; " + kind + "; " + provenance
   )
+  //TODO: possibly barrier models?
 }
 
 /** Holds if a neutral model exists for the given parameters. */
@@ -292,6 +312,7 @@ predicate modelCoverage(string package, int pkgs, string kind, string part, int
         summaryModel(subpkg, type, subtypes, name, signature, ext, input, output, kind, provenance,
           _)
       )
+    // TODO: possibly barrier models?
   )
 }
 
@@ -303,7 +324,9 @@ module ModelValidation {
     summaryModel(_, _, _, _, _, _, path, _, _, _, _) or
     summaryModel(_, _, _, _, _, _, _, path, _, _, _) or
     sinkModel(_, _, _, _, _, _, path, _, _, _) or
-    sourceModel(_, _, _, _, _, _, path, _, _, _)
+    sourceModel(_, _, _, _, _, _, path, _, _, _) or
+    barrierModel(_, _, _, _, _, _, path, _, _, _) or
+    barrierGuardModel(_, _, _, _, _, _, path, _, _, _, _)
   }
 
   private module MkAccessPath = AccessPathSyntax::AccessPath<getRelevantAccessPath/1>;
@@ -316,6 +339,8 @@ module ModelValidation {
     exists(string pred, AccessPath input, AccessPathToken part |
       sinkModel(_, _, _, _, _, _, input, _, _, _) and pred = "sink"
       or
+      barrierGuardModel(_, _, _, _, _, _, input, _, _, _, _) and pred = "barrier guard"
+      or
       summaryModel(_, _, _, _, _, _, input, _, _, _, _) and pred = "summary"
     |
       (
@@ -338,6 +363,8 @@ module ModelValidation {
     exists(string pred, AccessPath output, AccessPathToken part |
       sourceModel(_, _, _, _, _, _, output, _, _, _) and pred = "source"
       or
+      barrierModel(_, _, _, _, _, _, output, _, _, _) and pred = "barrier"
+      or
       summaryModel(_, _, _, _, _, _, _, output, _, _, _) and pred = "summary"
     |
       (
@@ -355,7 +382,13 @@ module ModelValidation {
   private module KindValConfig implements SharedModelVal::KindValidationConfigSig {
     predicate summaryKind(string kind) { summaryModel(_, _, _, _, _, _, _, _, kind, _, _) }
 
-    predicate sinkKind(string kind) { sinkModel(_, _, _, _, _, _, _, kind, _, _) }
+    predicate sinkKind(string kind) {
+      sinkModel(_, _, _, _, _, _, _, kind, _, _)
+      or
+      barrierModel(_, _, _, _, _, _, _, kind, _, _)
+      or
+      barrierGuardModel(_, _, _, _, _, _, _, _, kind, _, _)
+    }
 
     predicate sourceKind(string kind) { sourceModel(_, _, _, _, _, _, _, kind, _, _) }
 
@@ -373,6 +406,11 @@ module ModelValidation {
       or
       sinkModel(package, type, _, name, signature, ext, _, _, provenance, _) and pred = "sink"
       or
+      barrierModel(package, type, _, name, signature, ext, _, _, provenance, _) and pred = "barrier"
+      or
+      barrierGuardModel(package, type, _, name, signature, ext, _, _, _, provenance, _) and
+      pred = "barrier guard"
+      or
       summaryModel(package, type, _, name, signature, ext, _, _, _, provenance, _) and
       pred = "summary"
       or
@@ -398,6 +436,14 @@ module ModelValidation {
       invalidProvenance(provenance) and
       result = "Unrecognized provenance description \"" + provenance + "\" in " + pred + " model."
     )
+    or
+    exists(string acceptingvalue |
+      barrierGuardModel(_, _, _, _, _, _, _, acceptingvalue, _, _, _) and
+      invalidAcceptingValue(acceptingvalue) and
+      result =
+        "Unrecognized accepting value description \"" + acceptingvalue +
+          "\" in barrier guard model."
+    )
   }
 
   /** Holds if some row in a MaD flow model appears to contain typos. */
@@ -418,6 +464,10 @@ private predicate elementSpec(
   or
   sinkModel(package, type, subtypes, name, signature, ext, _, _, _, _)
   or
+  barrierModel(package, type, subtypes, name, signature, ext, _, _, _, _)
+  or
+  barrierGuardModel(package, type, subtypes, name, signature, ext, _, _, _, _, _)
+  or
   summaryModel(package, type, subtypes, name, signature, ext, _, _, _, _, _)
   or
   neutralModel(package, type, name, signature, _, _) and ext = "" and subtypes = true
@@ -578,6 +628,53 @@ private module Cached {
       isSinkNode(n, kind, model) and n.asNode() = node
     )
   }
+
+  private newtype TKindModelPair =
+    TMkPair(string kind, string model) { isBarrierGuardNode(_, _, kind, model) }
+
+  private GuardValue convertAcceptingValue(AcceptingValue av) {
+    av.isTrue() and result.asBooleanValue() = true
+    or
+    av.isFalse() and result.asBooleanValue() = false
+    or
+    av.isNoException() and result.getDualValue().isThrowsException()
+    or
+    av.isZero() and result.asIntValue() = 0
+    or
+    av.isNotZero() and result.getDualValue().asIntValue() = 0
+    or
+    av.isNull() and result.isNullValue()
+    or
+    av.isNotNull() and result.isNonNullValue()
+  }
+
+  private predicate barrierGuardChecks(Guard g, Expr e, GuardValue gv, TKindModelPair kmp) {
+    exists(
+      SourceSinkInterpretationInput::InterpretNode n, AcceptingValue acceptingvalue, string kind,
+      string model
+    |
+      isBarrierGuardNode(n, acceptingvalue, kind, model) and
+      n.asNode().asExpr() = e and
+      kmp = TMkPair(kind, model) and
+      gv = convertAcceptingValue(acceptingvalue)
+    |
+      g.(Call).getAnArgument() = e or g.(MethodCall).getQualifier() = e
+    )
+  }
+
+  /**
+   * Holds if `node` is specified as a barrier with the given kind in a MaD flow
+   * model.
+   */
+  cached
+  predicate barrierNode(Node node, string kind, string model) {
+    exists(SourceSinkInterpretationInput::InterpretNode n |
+      isBarrierNode(n, kind, model) and n.asNode() = node
+    )
+    or
+    ParameterizedBarrierGuard<TKindModelPair, barrierGuardChecks/4>::getABarrierNode(TMkPair(kind,
+        model)) = node
+  }
 }
 
 import Cached
@@ -594,6 +691,12 @@ predicate sourceNode(Node node, string kind) { sourceNode(node, kind, _) }
  */
 predicate sinkNode(Node node, string kind) { sinkNode(node, kind, _) }
 
+/**
+ * Holds if `node` is specified as a barrier with the given kind in a MaD flow
+ * model.
+ */
+predicate barrierNode(Node node, string kind) { barrierNode(node, kind, _) }
+
 // adapter class for converting Mad summaries to `SummarizedCallable`s
 private class SummarizedCallableAdapter extends SummarizedCallable {
   SummarizedCallableAdapter() { summaryElement(this, _, _, _, _, _, _) }
diff --git a/java/ql/lib/semmle/code/java/dataflow/internal/DataFlowUtil.qll b/java/ql/lib/semmle/code/java/dataflow/internal/DataFlowUtil.qll
index d96834a55331..e2e80c293ef0 100644
--- a/java/ql/lib/semmle/code/java/dataflow/internal/DataFlowUtil.qll
+++ b/java/ql/lib/semmle/code/java/dataflow/internal/DataFlowUtil.qll
@@ -420,3 +420,31 @@ module BarrierGuard<guardChecksSig/3 guardChecks> {
   /** Gets a node that is safely guarded by the given guard check. */
   Node getABarrierNode() { result = BarrierGuardValue<guardChecks0/3>::getABarrierNode() }
 }
+
+bindingset[this]
+private signature class ParamSig;
+
+private module WithParam<ParamSig P> {
+  /**
+   * Holds if the guard `g` validates the expression `e` upon evaluating to `gv`.
+   *
+   * The expression `e` is expected to be a syntactic part of the guard `g`.
+   * For example, the guard `g` might be a call `isSafe(x)` and the expression `e`
+   * the argument `x`.
+   */
+  signature predicate guardChecksSig(Guard g, Expr e, GuardValue gv, P param);
+}
+
+/**
+ * Provides a set of barrier nodes for a guard that validates an expression.
+ *
+ * This is expected to be used in `isBarrier`/`isSanitizer` definitions
+ * in data flow and taint tracking.
+ */
+module ParameterizedBarrierGuard<ParamSig P, WithParam<P>::guardChecksSig/4 guardChecks> {
+  /** Gets a node that is safely guarded by the given guard check. */
+  Node getABarrierNode(P param) {
+    SsaFlow::asNode(result) =
+      SsaImpl::DataFlowIntegration::ParameterizedBarrierGuard<P, guardChecks/4>::getABarrierNode(param)
+  }
+}
diff --git a/java/ql/lib/semmle/code/java/dataflow/internal/ExternalFlowExtensions.qll b/java/ql/lib/semmle/code/java/dataflow/internal/ExternalFlowExtensions.qll
index 32b5d289e28c..5386d916e240 100644
--- a/java/ql/lib/semmle/code/java/dataflow/internal/ExternalFlowExtensions.qll
+++ b/java/ql/lib/semmle/code/java/dataflow/internal/ExternalFlowExtensions.qll
@@ -20,6 +20,22 @@ extensible predicate sinkModel(
   string input, string kind, string provenance, QlBuiltins::ExtensionId madId
 );
 
+/**
+ * Holds if a barrier model exists for the given parameters.
+ */
+extensible predicate barrierModel(
+  string package, string type, boolean subtypes, string name, string signature, string ext,
+  string output, string kind, string provenance, QlBuiltins::ExtensionId madId
+);
+
+/**
+ * Holds if a barrier guard model exists for the given parameters.
+ */
+extensible predicate barrierGuardModel(
+  string package, string type, boolean subtypes, string name, string signature, string ext,
+  string input, string acceptingvalue, string kind, string provenance, QlBuiltins::ExtensionId madId
+);
+
 /**
  * Holds if a summary model exists for the given parameters.
  */
diff --git a/java/ql/lib/semmle/code/java/dataflow/internal/FlowSummaryImpl.qll b/java/ql/lib/semmle/code/java/dataflow/internal/FlowSummaryImpl.qll
index 8dc28ea2f601..19d9a33328b8 100644
--- a/java/ql/lib/semmle/code/java/dataflow/internal/FlowSummaryImpl.qll
+++ b/java/ql/lib/semmle/code/java/dataflow/internal/FlowSummaryImpl.qll
@@ -158,7 +158,9 @@ private predicate relatedArgSpec(Callable c, string spec) {
     summaryModel(namespace, type, subtypes, name, signature, ext, spec, _, _, _, _) or
     summaryModel(namespace, type, subtypes, name, signature, ext, _, spec, _, _, _) or
     sourceModel(namespace, type, subtypes, name, signature, ext, spec, _, _, _) or
-    sinkModel(namespace, type, subtypes, name, signature, ext, spec, _, _, _)
+    sinkModel(namespace, type, subtypes, name, signature, ext, spec, _, _, _) or
+    barrierModel(namespace, type, subtypes, name, signature, ext, spec, _, _, _) or
+    barrierGuardModel(namespace, type, subtypes, name, signature, ext, spec, _, _, _, _)
   |
     c = interpretElement(namespace, type, subtypes, name, signature, ext, _)
   )
@@ -259,6 +261,45 @@ module SourceSinkInterpretationInput implements
     )
   }
 
+  predicate barrierElement(
+    Element e, string output, string kind, Public::Provenance provenance, string model
+  ) {
+    exists(
+      string namespace, string type, boolean subtypes, string name, string signature, string ext,
+      SourceOrSinkElement baseBarrier, string originalOutput, QlBuiltins::ExtensionId madId
+    |
+      barrierModel(namespace, type, subtypes, name, signature, ext, originalOutput, kind,
+        provenance, madId) and
+      model = "MaD:" + madId.toString() and
+      baseBarrier = interpretElement(namespace, type, subtypes, name, signature, ext, _) and
+      (
+        e = baseBarrier and output = originalOutput
+        or
+        correspondingKotlinParameterDefaultsArgSpec(baseBarrier, e, originalOutput, output)
+      )
+    )
+  }
+
+  predicate barrierGuardElement(
+    Element e, string output, Public::AcceptingValue acceptingvalue, string kind,
+    Public::Provenance provenance, string model
+  ) {
+    exists(
+      string namespace, string type, boolean subtypes, string name, string signature, string ext,
+      SourceOrSinkElement baseBarrier, string originalOutput, QlBuiltins::ExtensionId madId
+    |
+      barrierGuardModel(namespace, type, subtypes, name, signature, ext, originalOutput,
+        acceptingvalue, kind, provenance, madId) and
+      model = "MaD:" + madId.toString() and
+      baseBarrier = interpretElement(namespace, type, subtypes, name, signature, ext, _) and
+      (
+        e = baseBarrier and output = originalOutput
+        or
+        correspondingKotlinParameterDefaultsArgSpec(baseBarrier, e, originalOutput, output)
+      )
+    )
+  }
+
   class SourceOrSinkElement = Element;
 
   private newtype TInterpretNode =
diff --git a/java/ql/lib/semmle/code/java/dataflow/internal/SsaImpl.qll b/java/ql/lib/semmle/code/java/dataflow/internal/SsaImpl.qll
index 323f14f550ff..bafb16d6ab53 100644
--- a/java/ql/lib/semmle/code/java/dataflow/internal/SsaImpl.qll
+++ b/java/ql/lib/semmle/code/java/dataflow/internal/SsaImpl.qll
@@ -588,6 +588,36 @@ private module Cached {
 
       predicate getABarrierNode = getABarrierNodeImpl/0;
     }
+
+    bindingset[this]
+    private signature class ParamSig;
+
+    private module WithParam<ParamSig P> {
+      signature predicate guardChecksSig(Guards::Guard g, Expr e, Guards::GuardValue gv, P param);
+    }
+
+    cached // nothing is actually cached
+    module ParameterizedBarrierGuard<ParamSig P, WithParam<P>::guardChecksSig/4 guardChecks> {
+      private predicate guardChecksAdjTypes(
+        Guards::Guards_v3::Guard g, Expr e, Guards::GuardValue gv, P param
+      ) {
+        guardChecks(g, e, gv, param)
+      }
+
+      private predicate guardChecksWithWrappers(
+        DataFlowIntegrationInput::Guard g, Definition def, Guards::GuardValue val, P param
+      ) {
+        Guards::Guards_v3::ParameterizedValidationWrapper<P, guardChecksAdjTypes/4>::guardChecksDef(g,
+          def, val, param)
+      }
+
+      private Node getABarrierNodeImpl(P param) {
+        result =
+          DataFlowIntegrationImpl::BarrierGuardDefWithState<P, guardChecksWithWrappers/4>::getABarrierNode(param)
+      }
+
+      predicate getABarrierNode = getABarrierNodeImpl/1;
+    }
   }
 
   cached
diff --git a/java/ql/lib/semmle/code/java/frameworks/hudson/Hudson.qll b/java/ql/lib/semmle/code/java/frameworks/hudson/Hudson.qll
index 44752f94576b..86b659289171 100644
--- a/java/ql/lib/semmle/code/java/frameworks/hudson/Hudson.qll
+++ b/java/ql/lib/semmle/code/java/frameworks/hudson/Hudson.qll
@@ -14,14 +14,3 @@ class HudsonWebMethod extends Method {
     this.getDeclaringType().getASourceSupertype*().hasQualifiedName("hudson.model", "Descriptor")
   }
 }
-
-private class HudsonUtilXssSanitizer extends XssSanitizer {
-  HudsonUtilXssSanitizer() {
-    this.asExpr()
-        .(MethodCall)
-        .getMethod()
-        // Not including xmlEscape because it only accounts for >, <, and &.
-        // It does not account for ", or ', which makes it an incomplete XSS sanitizer.
-        .hasQualifiedName("hudson", "Util", "escape")
-  }
-}
diff --git a/java/ql/lib/semmle/code/java/frameworks/owasp/Esapi.qll b/java/ql/lib/semmle/code/java/frameworks/owasp/Esapi.qll
deleted file mode 100644
index fe95cd0d39d3..000000000000
--- a/java/ql/lib/semmle/code/java/frameworks/owasp/Esapi.qll
+++ /dev/null
@@ -1,42 +0,0 @@
-/** Classes and predicates for reasoning about the `owasp.easpi` package. */
-overlay[local?]
-module;
-
-import java
-
-/**
- * The `org.owasp.esapi.Validator` interface.
- */
-class EsapiValidator extends RefType {
-  EsapiValidator() { this.hasQualifiedName("org.owasp.esapi", "Validator") }
-}
-
-/**
- * The methods of `org.owasp.esapi.Validator` which validate data.
- */
-class EsapiIsValidMethod extends Method {
-  EsapiIsValidMethod() {
-    this.getDeclaringType() instanceof EsapiValidator and
-    this.hasName([
-        "isValidCreditCard", "isValidDate", "isValidDirectoryPath", "isValidDouble",
-        "isValidFileContent", "isValidFileName", "isValidInput", "isValidInteger",
-        "isValidListItem", "isValidNumber", "isValidPrintable", "isValidRedirectLocation",
-        "isValidSafeHTML", "isValidURI"
-      ])
-  }
-}
-
-/**
- * The methods of `org.owasp.esapi.Validator` which return validated data.
- */
-class EsapiGetValidMethod extends Method {
-  EsapiGetValidMethod() {
-    this.getDeclaringType() instanceof EsapiValidator and
-    this.hasName([
-        "getValidCreditCard", "getValidDate", "getValidDirectoryPath", "getValidDouble",
-        "getValidFileContent", "getValidFileName", "getValidInput", "getValidInteger",
-        "getValidListItem", "getValidNumber", "getValidPrintable", "getValidRedirectLocation",
-        "getValidSafeHTML", "getValidURI"
-      ])
-  }
-}
diff --git a/java/ql/lib/semmle/code/java/security/PathSanitizer.qll b/java/ql/lib/semmle/code/java/security/PathSanitizer.qll
index da6f242bde52..2018004a3fb5 100644
--- a/java/ql/lib/semmle/code/java/security/PathSanitizer.qll
+++ b/java/ql/lib/semmle/code/java/security/PathSanitizer.qll
@@ -4,6 +4,7 @@ module;
 
 import java
 private import semmle.code.java.controlflow.Guards
+private import semmle.code.java.dataflow.ExternalFlow
 private import semmle.code.java.dataflow.FlowSources
 private import semmle.code.java.dataflow.SSA
 private import semmle.code.java.frameworks.kotlin.IO
@@ -288,19 +289,8 @@ private Method getSourceMethod(Method m) {
   result = m
 }
 
-/**
- * A sanitizer that protects against path injection vulnerabilities
- * by extracting the final component of the user provided path.
- *
- * TODO: convert this class to models-as-data if sanitizer support is added
- */
-private class FileGetNameSanitizer extends PathInjectionSanitizer {
-  FileGetNameSanitizer() {
-    exists(MethodCall mc |
-      mc.getMethod().hasQualifiedName("java.io", "File", "getName") and
-      this.asExpr() = mc
-    )
-  }
+private class DefaultPathInjectionSanitizer extends PathInjectionSanitizer {
+  DefaultPathInjectionSanitizer() { barrierNode(this, "path-injection") }
 }
 
 /** Holds if `g` is a guard that checks for `..` components. */
diff --git a/java/ql/lib/semmle/code/java/security/RequestForgery.qll b/java/ql/lib/semmle/code/java/security/RequestForgery.qll
index 9e3dec003579..690e4f9315b9 100644
--- a/java/ql/lib/semmle/code/java/security/RequestForgery.qll
+++ b/java/ql/lib/semmle/code/java/security/RequestForgery.qll
@@ -118,25 +118,8 @@ private class ContainsUrlSanitizer extends RequestForgerySanitizer {
   }
 }
 
-/**
- * A check that the URL is relative, and therefore safe for URL redirects.
- */
-private predicate isRelativeUrlSanitizer(Guard guard, Expr e, boolean branch) {
-  guard =
-    any(MethodCall call |
-      call.getMethod().hasQualifiedName("java.net", "URI", "isAbsolute") and
-      e = call.getQualifier() and
-      branch = false
-    )
-}
-
-/**
- * A check that the URL is relative, and therefore safe for URL redirects.
- */
-private class RelativeUrlSanitizer extends RequestForgerySanitizer {
-  RelativeUrlSanitizer() {
-    this = DataFlow::BarrierGuard<isRelativeUrlSanitizer/3>::getABarrierNode()
-  }
+private class DefaultRequestForgerySanitizer extends RequestForgerySanitizer {
+  DefaultRequestForgerySanitizer() { barrierNode(this, "request-forgery") }
 }
 
 /**
diff --git a/java/ql/lib/semmle/code/java/security/TrustBoundaryViolationQuery.qll b/java/ql/lib/semmle/code/java/security/TrustBoundaryViolationQuery.qll
index b2f49834b5ab..477aeb48b64e 100644
--- a/java/ql/lib/semmle/code/java/security/TrustBoundaryViolationQuery.qll
+++ b/java/ql/lib/semmle/code/java/security/TrustBoundaryViolationQuery.qll
@@ -5,7 +5,6 @@ private import semmle.code.java.dataflow.DataFlow
 private import semmle.code.java.controlflow.Guards
 private import semmle.code.java.dataflow.ExternalFlow
 private import semmle.code.java.dataflow.FlowSources
-private import semmle.code.java.frameworks.owasp.Esapi
 private import semmle.code.java.security.Sanitizers
 
 /**
@@ -28,25 +27,8 @@ class TrustBoundaryViolationSink extends DataFlow::Node {
  */
 abstract class TrustBoundaryValidationSanitizer extends DataFlow::Node { }
 
-/**
- * A node validated by an OWASP ESAPI validation method.
- */
-private class EsapiValidatedInputSanitizer extends TrustBoundaryValidationSanitizer {
-  EsapiValidatedInputSanitizer() {
-    this = DataFlow::BarrierGuard<esapiIsValidData/3>::getABarrierNode() or
-    this.asExpr().(MethodCall).getMethod() instanceof EsapiGetValidMethod
-  }
-}
-
-/**
- * Holds if `g` is a guard that checks that `e` is valid data according to an OWASP ESAPI validation method.
- */
-private predicate esapiIsValidData(Guard g, Expr e, boolean branch) {
-  branch = true and
-  exists(MethodCall ma | ma.getMethod() instanceof EsapiIsValidMethod |
-    g = ma and
-    e = ma.getArgument(1)
-  )
+private class DefaultTrustBoundaryValidationSanitizer extends TrustBoundaryValidationSanitizer {
+  DefaultTrustBoundaryValidationSanitizer() { barrierNode(this, "trust-boundary-violation") }
 }
 
 /**
diff --git a/java/ql/lib/semmle/code/java/security/XSS.qll b/java/ql/lib/semmle/code/java/security/XSS.qll
index 990371cc8cfe..c131f868f36c 100644
--- a/java/ql/lib/semmle/code/java/security/XSS.qll
+++ b/java/ql/lib/semmle/code/java/security/XSS.qll
@@ -54,12 +54,24 @@ private class DefaultXssSink extends XssSink {
   }
 }
 
-/** A default sanitizer that considers numeric and boolean typed data safe for writing to output. */
 private class DefaultXssSanitizer extends XssSanitizer {
-  DefaultXssSanitizer() {
+  DefaultXssSanitizer() { barrierNode(this, ["html-injection", "js-injection"]) }
+}
+
+/** A sanitizer that considers numeric and boolean typed data safe for writing to output. */
+private class PrimitiveSanitizer extends XssSanitizer {
+  PrimitiveSanitizer() {
     this.getType() instanceof NumericType or
-    this.getType() instanceof BooleanType or
-    // Match `org.springframework.web.util.HtmlUtils.htmlEscape` and possibly other methods like it.
+    this.getType() instanceof BooleanType
+  }
+}
+
+/**
+ * A call to `org.springframework.web.util.HtmlUtils.htmlEscape`, or possibly
+ * other methods like it, considered as a sanitizer for XSS.
+ */
+private class HtmlEscapeXssSanitizer extends XssSanitizer {
+  HtmlEscapeXssSanitizer() {
     this.asExpr().(MethodCall).getMethod().getName().regexpMatch("(?i)html_?escape.*")
   }
 }
diff --git a/java/ql/lib/semmle/code/java/security/regexp/RegexInjection.qll b/java/ql/lib/semmle/code/java/security/regexp/RegexInjection.qll
index eb27ec873752..d91b411b7978 100644
--- a/java/ql/lib/semmle/code/java/security/regexp/RegexInjection.qll
+++ b/java/ql/lib/semmle/code/java/security/regexp/RegexInjection.qll
@@ -21,17 +21,8 @@ private class DefaultRegexInjectionSink extends RegexInjectionSink {
   }
 }
 
-/**
- * A call to the `Pattern.quote` method, which gives metacharacters or escape sequences
- * no special meaning.
- */
-private class PatternQuoteCall extends RegexInjectionSanitizer {
-  PatternQuoteCall() {
-    exists(MethodCall ma, Method m | m = ma.getMethod() |
-      ma.getArgument(0) = this.asExpr() and
-      m instanceof PatternQuoteMethod
-    )
-  }
+private class DefaultRegexInjectionSanitizer extends RegexInjectionSanitizer {
+  DefaultRegexInjectionSanitizer() { barrierNode(this, "regex-use") }
 }
 
 /**
diff --git a/javascript/ql/lib/semmle/javascript/frameworks/data/internal/ApiGraphModels.qll b/javascript/ql/lib/semmle/javascript/frameworks/data/internal/ApiGraphModels.qll
index 80ec45a3cf17..ee2cd8f57bfe 100644
--- a/javascript/ql/lib/semmle/javascript/frameworks/data/internal/ApiGraphModels.qll
+++ b/javascript/ql/lib/semmle/javascript/frameworks/data/internal/ApiGraphModels.qll
@@ -344,6 +344,26 @@ private predicate sinkModel(string type, string path, string kind, string model)
   )
 }
 
+/** Holds if a barrier model exists for the given parameters. */
+private predicate barrierModel(string type, string path, string kind, string model) {
+  // No deprecation adapter for barrier models, they were not around back then.
+  exists(QlBuiltins::ExtensionId madId |
+    Extensions::barrierModel(type, path, kind, madId) and
+    model = "MaD:" + madId.toString()
+  )
+}
+
+/** Holds if a barrier guard model exists for the given parameters. */
+private predicate barrierGuardModel(
+  string type, string path, string branch, string kind, string model
+) {
+  // No deprecation adapter for barrier models, they were not around back then.
+  exists(QlBuiltins::ExtensionId madId |
+    Extensions::barrierGuardModel(type, path, branch, kind, madId) and
+    model = "MaD:" + madId.toString()
+  )
+}
+
 /** Holds if a summary model `row` exists for the given parameters. */
 private predicate summaryModel(
   string type, string path, string input, string output, string kind, string model
@@ -400,6 +420,8 @@ predicate isRelevantType(string type) {
   (
     sourceModel(type, _, _, _) or
     sinkModel(type, _, _, _) or
+    barrierModel(type, _, _, _) or
+    barrierGuardModel(type, _, _, _, _) or
     summaryModel(type, _, _, _, _, _) or
     typeModel(_, type, _)
   ) and
@@ -427,6 +449,8 @@ predicate isRelevantFullPath(string type, string path) {
   (
     sourceModel(type, path, _, _) or
     sinkModel(type, path, _, _) or
+    barrierModel(type, path, _, _) or
+    barrierGuardModel(type, path, _, _, _) or
     summaryModel(type, path, _, _, _, _) or
     typeModel(_, type, path)
   )
@@ -745,6 +769,32 @@ module ModelOutput {
       )
     }
 
+    /**
+     * Holds if a barrier model contributed `barrier` with the given `kind`.
+     */
+    cached
+    API::Node getABarrierNode(string kind, string model) {
+      exists(string type, string path |
+        barrierModel(type, path, kind, model) and
+        result = getNodeFromPath(type, path)
+      )
+    }
+
+    /**
+     * Holds if a barrier model contributed `barrier` with the given `kind`.
+     */
+    cached
+    API::Node getABarrierGuardNode(string kind, boolean branch, string model) {
+      exists(string type, string path, string branch_str |
+        branch = true and branch_str = "true"
+        or
+        branch = false and branch_str = "false"
+      |
+        barrierGuardModel(type, path, branch_str, kind, model) and
+        result = getNodeFromPath(type, path)
+      )
+    }
+
     /**
      * Holds if a relevant summary exists for these parameters.
      */
@@ -787,15 +837,27 @@ module ModelOutput {
   private import codeql.mad.ModelValidation as SharedModelVal
 
   /**
-   * Holds if a CSV source model contributed `source` with the given `kind`.
+   * Holds if an external model contributed `source` with the given `kind`.
    */
   API::Node getASourceNode(string kind) { result = getASourceNode(kind, _) }
 
   /**
-   * Holds if a CSV sink model contributed `sink` with the given `kind`.
+   * Holds if an external model contributed `sink` with the given `kind`.
    */
   API::Node getASinkNode(string kind) { result = getASinkNode(kind, _) }
 
+  /**
+   * Holds if an external model contributed `barrier` with the given `kind`.
+   */
+  API::Node getABarrierNode(string kind) { result = getABarrierNode(kind, _) }
+
+  /**
+   * Holds if an external model contributed `barrier-guard` with the given `kind` and `branch`.
+   */
+  API::Node getABarrierGuardNode(string kind, boolean branch) {
+    result = getABarrierGuardNode(kind, branch, _)
+  }
+
   private module KindValConfig implements SharedModelVal::KindValidationConfigSig {
     predicate summaryKind(string kind) { summaryModel(_, _, _, _, kind, _) }
 
diff --git a/javascript/ql/lib/semmle/javascript/frameworks/data/internal/ApiGraphModelsExtensions.qll b/javascript/ql/lib/semmle/javascript/frameworks/data/internal/ApiGraphModelsExtensions.qll
index 3f38c498f324..2a644aabb95d 100644
--- a/javascript/ql/lib/semmle/javascript/frameworks/data/internal/ApiGraphModelsExtensions.qll
+++ b/javascript/ql/lib/semmle/javascript/frameworks/data/internal/ApiGraphModelsExtensions.qll
@@ -20,6 +20,26 @@ extensible predicate sourceModel(
  */
 extensible predicate sinkModel(string type, string path, string kind, QlBuiltins::ExtensionId madId);
 
+/**
+ * Holds if the value at `(type, path)` should be seen as a barrier
+ * of the given `kind` and `madId` is the data extension row number.
+ */
+extensible predicate barrierModel(
+  string type, string path, string kind, QlBuiltins::ExtensionId madId
+);
+
+/**
+ * Holds if the value at `(type, path)` should be seen as a barrier guard
+ * of the given `kind` and `madId` is the data extension row number.
+ * `path` is assumed to lead to a parameter of a call (possibly `self`), and
+ * the call is guarding the parameter.
+ * `branch` is either `true` or `false`, indicating which branch of the guard
+ * is protecting the parameter.
+ */
+extensible predicate barrierGuardModel(
+  string type, string path, string branch, string kind, QlBuiltins::ExtensionId madId
+);
+
 /**
  * Holds if in calls to `(type, path)`, the value referred to by `input`
  * can flow to the value referred to by `output` and `madId` is the data
diff --git a/javascript/ql/lib/semmle/javascript/frameworks/data/internal/empty.model.yml b/javascript/ql/lib/semmle/javascript/frameworks/data/internal/empty.model.yml
index 12f83f71e55b..6542a1194cab 100644
--- a/javascript/ql/lib/semmle/javascript/frameworks/data/internal/empty.model.yml
+++ b/javascript/ql/lib/semmle/javascript/frameworks/data/internal/empty.model.yml
@@ -16,6 +16,16 @@ extensions:
       extensible: summaryModel
     data: []
 
+  - addsTo:
+      pack: codeql/javascript-all
+      extensible: barrierModel
+    data: []
+
+  - addsTo:
+      pack: codeql/javascript-all
+      extensible: barrierGuardModel
+    data: []
+
   - addsTo:
       pack: codeql/javascript-all
       extensible: neutralModel
diff --git a/python/ql/lib/semmle/python/dataflow/new/internal/DataFlowPublic.qll b/python/ql/lib/semmle/python/dataflow/new/internal/DataFlowPublic.qll
index ffecbcba57ac..65e03963379a 100644
--- a/python/ql/lib/semmle/python/dataflow/new/internal/DataFlowPublic.qll
+++ b/python/ql/lib/semmle/python/dataflow/new/internal/DataFlowPublic.qll
@@ -600,15 +600,64 @@ signature predicate guardChecksSig(GuardNode g, ControlFlowNode node, boolean br
 module BarrierGuard<guardChecksSig/3 guardChecks> {
   /** Gets a node that is safely guarded by the given guard check. */
   ExprNode getABarrierNode() {
+    result = ParameterizedBarrierGuard<Unit, extendedGuardChecks/4>::getABarrierNode(_)
+  }
+
+  private predicate extendedGuardChecks(GuardNode g, ControlFlowNode node, boolean branch, Unit u) {
+    guardChecks(g, node, branch)
+  }
+}
+
+bindingset[this]
+private signature class ParamSig;
+
+private module WithParam<ParamSig P> {
+  signature predicate guardChecksSig(GuardNode g, ControlFlowNode node, boolean branch, P param);
+}
+
+/**
+ * Provides a set of barrier nodes for a guard that validates a node.
+ *
+ * This is expected to be used in `isBarrier`/`isSanitizer` definitions
+ * in data flow and taint tracking.
+ */
+module ParameterizedBarrierGuard<ParamSig P, WithParam<P>::guardChecksSig/4 guardChecks> {
+  /** Gets a node that is safely guarded by the given guard check with parameter `param`. */
+  ExprNode getABarrierNode(P param) {
     exists(GuardNode g, EssaDefinition def, ControlFlowNode node, boolean branch |
       AdjacentUses::useOfDef(def, node) and
-      guardChecks(g, node, branch) and
+      guardChecks(g, node, branch, param) and
       AdjacentUses::useOfDef(def, result.asCfgNode()) and
       g.controlsBlock(result.asCfgNode().getBasicBlock(), branch)
     )
   }
 }
 
+/**
+ * Provides a set of barrier nodes for a guard that validates a node as described by an external predicate.
+ *
+ * This is expected to be used in `isBarrier`/`isSanitizer` definitions
+ * in data flow and taint tracking.
+ */
+module ExternalBarrierGuard {
+  private import semmle.python.ApiGraphs
+
+  private predicate guardCheck(GuardNode g, ControlFlowNode node, boolean branch, string kind) {
+    exists(API::CallNode call, API::Node parameter |
+      parameter = call.getAParameter() and
+      parameter = ModelOutput::getABarrierGuardNode(kind, branch)
+    |
+      g = call.asCfgNode() and
+      node = parameter.asSink().asCfgNode()
+    )
+  }
+
+  /** Gets a node that is an external barrier of the given kind. */
+  ExprNode getAnExternalBarrierNode(string kind) {
+    result = ParameterizedBarrierGuard<string, guardCheck/4>::getABarrierNode(kind)
+  }
+}
+
 /**
  * Algebraic datatype for tracking data content associated with values.
  * Content can be collection elements or object attributes.
diff --git a/python/ql/lib/semmle/python/frameworks/Django.model.yml b/python/ql/lib/semmle/python/frameworks/Django.model.yml
new file mode 100644
index 000000000000..4e472af6c117
--- /dev/null
+++ b/python/ql/lib/semmle/python/frameworks/Django.model.yml
@@ -0,0 +1,6 @@
+extensions:
+  - addsTo:
+      pack: codeql/python-all
+      extensible: barrierGuardModel
+    data:
+      - ['django', 'Member[utils].Member[http].Member[url_has_allowed_host_and_scheme].Argument[0,url:]', "true", 'url-redirection']
diff --git a/python/ql/lib/semmle/python/frameworks/Django.qll b/python/ql/lib/semmle/python/frameworks/Django.qll
index 4aa5776ad54b..ee0ed4a84dd0 100644
--- a/python/ql/lib/semmle/python/frameworks/Django.qll
+++ b/python/ql/lib/semmle/python/frameworks/Django.qll
@@ -2965,38 +2965,6 @@ module PrivateDjango {
     override predicate csrfEnabled() { decoratorName in ["csrf_protect", "requires_csrf_token"] }
   }
 
-  private predicate djangoUrlHasAllowedHostAndScheme(
-    DataFlow::GuardNode g, ControlFlowNode node, boolean branch
-  ) {
-    exists(API::CallNode call |
-      call =
-        API::moduleImport("django")
-            .getMember("utils")
-            .getMember("http")
-            .getMember("url_has_allowed_host_and_scheme")
-            .getACall() and
-      g = call.asCfgNode() and
-      node = call.getParameter(0, "url").asSink().asCfgNode() and
-      branch = true
-    )
-  }
-
-  /**
-   * A call to `django.utils.http.url_has_allowed_host_and_scheme`, considered as a sanitizer-guard for URL redirection.
-   *
-   * See https://docs.djangoproject.com/en/4.2/_modules/django/utils/http/
-   */
-  private class DjangoAllowedUrl extends UrlRedirect::Sanitizer {
-    DjangoAllowedUrl() {
-      this = DataFlow::BarrierGuard<djangoUrlHasAllowedHostAndScheme/3>::getABarrierNode()
-    }
-
-    override predicate sanitizes(UrlRedirect::FlowState state) {
-      // sanitize all flow states
-      any()
-    }
-  }
-
   // ---------------------------------------------------------------------------
   // Templates
   // ---------------------------------------------------------------------------
diff --git a/python/ql/lib/semmle/python/frameworks/data/internal/ApiGraphModels.qll b/python/ql/lib/semmle/python/frameworks/data/internal/ApiGraphModels.qll
index 80ec45a3cf17..ee2cd8f57bfe 100644
--- a/python/ql/lib/semmle/python/frameworks/data/internal/ApiGraphModels.qll
+++ b/python/ql/lib/semmle/python/frameworks/data/internal/ApiGraphModels.qll
@@ -344,6 +344,26 @@ private predicate sinkModel(string type, string path, string kind, string model)
   )
 }
 
+/** Holds if a barrier model exists for the given parameters. */
+private predicate barrierModel(string type, string path, string kind, string model) {
+  // No deprecation adapter for barrier models, they were not around back then.
+  exists(QlBuiltins::ExtensionId madId |
+    Extensions::barrierModel(type, path, kind, madId) and
+    model = "MaD:" + madId.toString()
+  )
+}
+
+/** Holds if a barrier guard model exists for the given parameters. */
+private predicate barrierGuardModel(
+  string type, string path, string branch, string kind, string model
+) {
+  // No deprecation adapter for barrier models, they were not around back then.
+  exists(QlBuiltins::ExtensionId madId |
+    Extensions::barrierGuardModel(type, path, branch, kind, madId) and
+    model = "MaD:" + madId.toString()
+  )
+}
+
 /** Holds if a summary model `row` exists for the given parameters. */
 private predicate summaryModel(
   string type, string path, string input, string output, string kind, string model
@@ -400,6 +420,8 @@ predicate isRelevantType(string type) {
   (
     sourceModel(type, _, _, _) or
     sinkModel(type, _, _, _) or
+    barrierModel(type, _, _, _) or
+    barrierGuardModel(type, _, _, _, _) or
     summaryModel(type, _, _, _, _, _) or
     typeModel(_, type, _)
   ) and
@@ -427,6 +449,8 @@ predicate isRelevantFullPath(string type, string path) {
   (
     sourceModel(type, path, _, _) or
     sinkModel(type, path, _, _) or
+    barrierModel(type, path, _, _) or
+    barrierGuardModel(type, path, _, _, _) or
     summaryModel(type, path, _, _, _, _) or
     typeModel(_, type, path)
   )
@@ -745,6 +769,32 @@ module ModelOutput {
       )
     }
 
+    /**
+     * Holds if a barrier model contributed `barrier` with the given `kind`.
+     */
+    cached
+    API::Node getABarrierNode(string kind, string model) {
+      exists(string type, string path |
+        barrierModel(type, path, kind, model) and
+        result = getNodeFromPath(type, path)
+      )
+    }
+
+    /**
+     * Holds if a barrier model contributed `barrier` with the given `kind`.
+     */
+    cached
+    API::Node getABarrierGuardNode(string kind, boolean branch, string model) {
+      exists(string type, string path, string branch_str |
+        branch = true and branch_str = "true"
+        or
+        branch = false and branch_str = "false"
+      |
+        barrierGuardModel(type, path, branch_str, kind, model) and
+        result = getNodeFromPath(type, path)
+      )
+    }
+
     /**
      * Holds if a relevant summary exists for these parameters.
      */
@@ -787,15 +837,27 @@ module ModelOutput {
   private import codeql.mad.ModelValidation as SharedModelVal
 
   /**
-   * Holds if a CSV source model contributed `source` with the given `kind`.
+   * Holds if an external model contributed `source` with the given `kind`.
    */
   API::Node getASourceNode(string kind) { result = getASourceNode(kind, _) }
 
   /**
-   * Holds if a CSV sink model contributed `sink` with the given `kind`.
+   * Holds if an external model contributed `sink` with the given `kind`.
    */
   API::Node getASinkNode(string kind) { result = getASinkNode(kind, _) }
 
+  /**
+   * Holds if an external model contributed `barrier` with the given `kind`.
+   */
+  API::Node getABarrierNode(string kind) { result = getABarrierNode(kind, _) }
+
+  /**
+   * Holds if an external model contributed `barrier-guard` with the given `kind` and `branch`.
+   */
+  API::Node getABarrierGuardNode(string kind, boolean branch) {
+    result = getABarrierGuardNode(kind, branch, _)
+  }
+
   private module KindValConfig implements SharedModelVal::KindValidationConfigSig {
     predicate summaryKind(string kind) { summaryModel(_, _, _, _, kind, _) }
 
diff --git a/python/ql/lib/semmle/python/frameworks/data/internal/ApiGraphModelsExtensions.qll b/python/ql/lib/semmle/python/frameworks/data/internal/ApiGraphModelsExtensions.qll
index 3f38c498f324..2a644aabb95d 100644
--- a/python/ql/lib/semmle/python/frameworks/data/internal/ApiGraphModelsExtensions.qll
+++ b/python/ql/lib/semmle/python/frameworks/data/internal/ApiGraphModelsExtensions.qll
@@ -20,6 +20,26 @@ extensible predicate sourceModel(
  */
 extensible predicate sinkModel(string type, string path, string kind, QlBuiltins::ExtensionId madId);
 
+/**
+ * Holds if the value at `(type, path)` should be seen as a barrier
+ * of the given `kind` and `madId` is the data extension row number.
+ */
+extensible predicate barrierModel(
+  string type, string path, string kind, QlBuiltins::ExtensionId madId
+);
+
+/**
+ * Holds if the value at `(type, path)` should be seen as a barrier guard
+ * of the given `kind` and `madId` is the data extension row number.
+ * `path` is assumed to lead to a parameter of a call (possibly `self`), and
+ * the call is guarding the parameter.
+ * `branch` is either `true` or `false`, indicating which branch of the guard
+ * is protecting the parameter.
+ */
+extensible predicate barrierGuardModel(
+  string type, string path, string branch, string kind, QlBuiltins::ExtensionId madId
+);
+
 /**
  * Holds if in calls to `(type, path)`, the value referred to by `input`
  * can flow to the value referred to by `output` and `madId` is the data
diff --git a/python/ql/lib/semmle/python/frameworks/data/internal/empty.model.yml b/python/ql/lib/semmle/python/frameworks/data/internal/empty.model.yml
index ea9b9fce546b..a7529031c29f 100644
--- a/python/ql/lib/semmle/python/frameworks/data/internal/empty.model.yml
+++ b/python/ql/lib/semmle/python/frameworks/data/internal/empty.model.yml
@@ -11,6 +11,16 @@ extensions:
       extensible: sinkModel
     data: []
 
+  - addsTo:
+      pack: codeql/python-all
+      extensible: barrierModel
+    data: []
+
+  - addsTo:
+      pack: codeql/python-all
+      extensible: barrierGuardModel
+    data: []
+
   - addsTo:
       pack: codeql/python-all
       extensible: summaryModel
diff --git a/python/ql/lib/semmle/python/security/dataflow/UrlRedirectCustomizations.qll b/python/ql/lib/semmle/python/security/dataflow/UrlRedirectCustomizations.qll
index f5810944f8d9..a1c652192f41 100644
--- a/python/ql/lib/semmle/python/security/dataflow/UrlRedirectCustomizations.qll
+++ b/python/ql/lib/semmle/python/security/dataflow/UrlRedirectCustomizations.qll
@@ -7,6 +7,7 @@
 private import python
 private import semmle.python.dataflow.new.DataFlow
 private import semmle.python.Concepts
+private import semmle.python.ApiGraphs
 private import semmle.python.dataflow.new.RemoteFlowSources
 private import semmle.python.dataflow.new.BarrierGuards
 private import semmle.python.frameworks.data.ModelsAsData
@@ -95,6 +96,9 @@ module UrlRedirect {
     }
   }
 
+  /**
+   * A sink for URL redirection defined via models-as-data.
+   */
   private class SinkFromModel extends Sink {
     SinkFromModel() { this = ModelOutput::getASinkNode("url-redirection").asSink() }
   }
@@ -156,4 +160,15 @@ module UrlRedirect {
 
   /** DEPRECATED: Use ConstCompareAsSanitizerGuard instead. */
   deprecated class StringConstCompareAsSanitizerGuard = ConstCompareAsSanitizerGuard;
+
+  class SanitizerFromModel extends Sanitizer {
+    SanitizerFromModel() {
+      this = DataFlow::ExternalBarrierGuard::getAnExternalBarrierNode("url-redirection")
+    }
+
+    override predicate sanitizes(FlowState state) {
+      // sanitize all flow states
+      any()
+    }
+  }
 }
diff --git a/python/ql/test/experimental/query-tests/Security/CWE-022-UnsafeUnpacking/UnsafeUnpack.expected b/python/ql/test/experimental/query-tests/Security/CWE-022-UnsafeUnpacking/UnsafeUnpack.expected
index 0f334d45ea83..69bb8d30e8f4 100644
--- a/python/ql/test/experimental/query-tests/Security/CWE-022-UnsafeUnpacking/UnsafeUnpack.expected
+++ b/python/ql/test/experimental/query-tests/Security/CWE-022-UnsafeUnpacking/UnsafeUnpack.expected
@@ -75,7 +75,7 @@ edges
 | UnsafeUnpack.py:161:19:161:21 | ControlFlowNode for tar | UnsafeUnpack.py:163:33:163:35 | ControlFlowNode for tar | provenance |  |
 | UnsafeUnpack.py:161:25:161:46 | ControlFlowNode for Attribute() | UnsafeUnpack.py:161:19:161:21 | ControlFlowNode for tar | provenance |  |
 | UnsafeUnpack.py:161:38:161:45 | ControlFlowNode for savepath | UnsafeUnpack.py:161:25:161:46 | ControlFlowNode for Attribute() | provenance | Config |
-| UnsafeUnpack.py:161:38:161:45 | ControlFlowNode for savepath | UnsafeUnpack.py:161:25:161:46 | ControlFlowNode for Attribute() | provenance | MaD:69 |
+| UnsafeUnpack.py:161:38:161:45 | ControlFlowNode for savepath | UnsafeUnpack.py:161:25:161:46 | ControlFlowNode for Attribute() | provenance | MaD:70 |
 | UnsafeUnpack.py:163:23:163:28 | ControlFlowNode for member | UnsafeUnpack.py:166:37:166:42 | ControlFlowNode for member | provenance |  |
 | UnsafeUnpack.py:163:33:163:35 | ControlFlowNode for tar | UnsafeUnpack.py:163:23:163:28 | ControlFlowNode for member | provenance |  |
 | UnsafeUnpack.py:166:23:166:28 | [post] ControlFlowNode for result | UnsafeUnpack.py:167:67:167:72 | ControlFlowNode for result | provenance |  |
diff --git a/python/ql/test/experimental/query-tests/Security/CWE-409/DecompressionBombs.expected b/python/ql/test/experimental/query-tests/Security/CWE-409/DecompressionBombs.expected
index 87b07df086fa..da68554f61db 100644
--- a/python/ql/test/experimental/query-tests/Security/CWE-409/DecompressionBombs.expected
+++ b/python/ql/test/experimental/query-tests/Security/CWE-409/DecompressionBombs.expected
@@ -1,23 +1,23 @@
 edges
 | test.py:10:16:10:24 | ControlFlowNode for file_path | test.py:11:21:11:29 | ControlFlowNode for file_path | provenance |  |
 | test.py:11:5:11:35 | ControlFlowNode for Attribute() | test.py:11:5:11:52 | ControlFlowNode for Attribute() | provenance | Config |
-| test.py:11:21:11:29 | ControlFlowNode for file_path | test.py:11:5:11:35 | ControlFlowNode for Attribute() | provenance | MaD:86 |
+| test.py:11:21:11:29 | ControlFlowNode for file_path | test.py:11:5:11:35 | ControlFlowNode for Attribute() | provenance | MaD:87 |
 | test.py:11:21:11:29 | ControlFlowNode for file_path | test.py:11:5:11:52 | ControlFlowNode for Attribute() | provenance | Config |
 | test.py:11:21:11:29 | ControlFlowNode for file_path | test.py:12:21:12:29 | ControlFlowNode for file_path | provenance |  |
 | test.py:12:5:12:35 | ControlFlowNode for Attribute() | test.py:12:5:12:48 | ControlFlowNode for Attribute() | provenance | Config |
-| test.py:12:21:12:29 | ControlFlowNode for file_path | test.py:12:5:12:35 | ControlFlowNode for Attribute() | provenance | MaD:86 |
+| test.py:12:21:12:29 | ControlFlowNode for file_path | test.py:12:5:12:35 | ControlFlowNode for Attribute() | provenance | MaD:87 |
 | test.py:12:21:12:29 | ControlFlowNode for file_path | test.py:12:5:12:48 | ControlFlowNode for Attribute() | provenance | Config |
 | test.py:12:21:12:29 | ControlFlowNode for file_path | test.py:14:26:14:34 | ControlFlowNode for file_path | provenance |  |
 | test.py:14:10:14:35 | ControlFlowNode for Attribute() | test.py:15:14:15:29 | ControlFlowNode for Attribute() | provenance | Config |
-| test.py:14:26:14:34 | ControlFlowNode for file_path | test.py:14:10:14:35 | ControlFlowNode for Attribute() | provenance | MaD:86 |
+| test.py:14:26:14:34 | ControlFlowNode for file_path | test.py:14:10:14:35 | ControlFlowNode for Attribute() | provenance | MaD:87 |
 | test.py:14:26:14:34 | ControlFlowNode for file_path | test.py:15:14:15:29 | ControlFlowNode for Attribute() | provenance | Config |
 | test.py:14:26:14:34 | ControlFlowNode for file_path | test.py:18:26:18:34 | ControlFlowNode for file_path | provenance |  |
 | test.py:18:10:18:35 | ControlFlowNode for Attribute() | test.py:19:14:19:39 | ControlFlowNode for Attribute() | provenance | Config |
-| test.py:18:26:18:34 | ControlFlowNode for file_path | test.py:18:10:18:35 | ControlFlowNode for Attribute() | provenance | MaD:86 |
+| test.py:18:26:18:34 | ControlFlowNode for file_path | test.py:18:10:18:35 | ControlFlowNode for Attribute() | provenance | MaD:87 |
 | test.py:18:26:18:34 | ControlFlowNode for file_path | test.py:19:14:19:39 | ControlFlowNode for Attribute() | provenance | Config |
 | test.py:18:26:18:34 | ControlFlowNode for file_path | test.py:22:21:22:29 | ControlFlowNode for file_path | provenance |  |
 | test.py:22:5:22:30 | ControlFlowNode for Attribute() | test.py:22:5:22:60 | ControlFlowNode for Attribute() | provenance | Config |
-| test.py:22:21:22:29 | ControlFlowNode for file_path | test.py:22:5:22:30 | ControlFlowNode for Attribute() | provenance | MaD:86 |
+| test.py:22:21:22:29 | ControlFlowNode for file_path | test.py:22:5:22:30 | ControlFlowNode for Attribute() | provenance | MaD:87 |
 | test.py:22:21:22:29 | ControlFlowNode for file_path | test.py:22:5:22:60 | ControlFlowNode for Attribute() | provenance | Config |
 | test.py:22:21:22:29 | ControlFlowNode for file_path | test.py:24:18:24:26 | ControlFlowNode for file_path | provenance |  |
 | test.py:24:18:24:26 | ControlFlowNode for file_path | test.py:24:5:24:52 | ControlFlowNode for Attribute() | provenance | Config |
diff --git a/python/ql/test/query-tests/Security/CWE-089-SqlInjection-local-threat-model/SqlInjection.expected b/python/ql/test/query-tests/Security/CWE-089-SqlInjection-local-threat-model/SqlInjection.expected
index 1e4ba8b95305..d59e639d641b 100644
--- a/python/ql/test/query-tests/Security/CWE-089-SqlInjection-local-threat-model/SqlInjection.expected
+++ b/python/ql/test/query-tests/Security/CWE-089-SqlInjection-local-threat-model/SqlInjection.expected
@@ -1,5 +1,5 @@
 edges
-| test.py:6:14:6:21 | ControlFlowNode for Attribute | test.py:6:14:6:24 | ControlFlowNode for Subscript | provenance | Src:MaD:17  |
+| test.py:6:14:6:21 | ControlFlowNode for Attribute | test.py:6:14:6:24 | ControlFlowNode for Subscript | provenance | Src:MaD:18  |
 nodes
 | test.py:6:14:6:21 | ControlFlowNode for Attribute | semmle.label | ControlFlowNode for Attribute |
 | test.py:6:14:6:24 | ControlFlowNode for Subscript | semmle.label | ControlFlowNode for Subscript |
diff --git a/python/ql/test/query-tests/Security/CWE-113-HeaderInjection/Tests1/HeaderInjection.expected b/python/ql/test/query-tests/Security/CWE-113-HeaderInjection/Tests1/HeaderInjection.expected
index cea505fe39db..6c5f8363c487 100644
--- a/python/ql/test/query-tests/Security/CWE-113-HeaderInjection/Tests1/HeaderInjection.expected
+++ b/python/ql/test/query-tests/Security/CWE-113-HeaderInjection/Tests1/HeaderInjection.expected
@@ -14,10 +14,10 @@ edges
 | http_test.py:5:16:5:19 | ControlFlowNode for self | http_test.py:6:45:6:53 | ControlFlowNode for Attribute | provenance | AdditionalTaintStep |
 | http_test.py:6:9:6:19 | ControlFlowNode for parsed_path | http_test.py:7:40:7:56 | ControlFlowNode for Attribute | provenance | AdditionalTaintStep |
 | http_test.py:6:23:6:54 | ControlFlowNode for Attribute() | http_test.py:6:9:6:19 | ControlFlowNode for parsed_path | provenance |  |
-| http_test.py:6:45:6:53 | ControlFlowNode for Attribute | http_test.py:6:23:6:54 | ControlFlowNode for Attribute() | provenance | MaD:77 |
+| http_test.py:6:45:6:53 | ControlFlowNode for Attribute | http_test.py:6:23:6:54 | ControlFlowNode for Attribute() | provenance | MaD:78 |
 | http_test.py:7:9:7:14 | ControlFlowNode for params | http_test.py:8:23:8:28 | ControlFlowNode for params | provenance |  |
 | http_test.py:7:18:7:57 | ControlFlowNode for Attribute() | http_test.py:7:9:7:14 | ControlFlowNode for params | provenance |  |
-| http_test.py:7:40:7:56 | ControlFlowNode for Attribute | http_test.py:7:18:7:57 | ControlFlowNode for Attribute() | provenance | MaD:76 |
+| http_test.py:7:40:7:56 | ControlFlowNode for Attribute | http_test.py:7:18:7:57 | ControlFlowNode for Attribute() | provenance | MaD:77 |
 | http_test.py:8:9:8:19 | ControlFlowNode for input_value | http_test.py:12:40:12:50 | ControlFlowNode for input_value | provenance |  |
 | http_test.py:8:23:8:28 | ControlFlowNode for params | http_test.py:8:23:8:47 | ControlFlowNode for Attribute() | provenance | dict.get |
 | http_test.py:8:23:8:47 | ControlFlowNode for Attribute() | http_test.py:8:9:8:19 | ControlFlowNode for input_value | provenance |  |
diff --git a/ruby/ql/lib/codeql/ruby/frameworks/data/internal/ApiGraphModels.qll b/ruby/ql/lib/codeql/ruby/frameworks/data/internal/ApiGraphModels.qll
index 80ec45a3cf17..ee2cd8f57bfe 100644
--- a/ruby/ql/lib/codeql/ruby/frameworks/data/internal/ApiGraphModels.qll
+++ b/ruby/ql/lib/codeql/ruby/frameworks/data/internal/ApiGraphModels.qll
@@ -344,6 +344,26 @@ private predicate sinkModel(string type, string path, string kind, string model)
   )
 }
 
+/** Holds if a barrier model exists for the given parameters. */
+private predicate barrierModel(string type, string path, string kind, string model) {
+  // No deprecation adapter for barrier models, they were not around back then.
+  exists(QlBuiltins::ExtensionId madId |
+    Extensions::barrierModel(type, path, kind, madId) and
+    model = "MaD:" + madId.toString()
+  )
+}
+
+/** Holds if a barrier guard model exists for the given parameters. */
+private predicate barrierGuardModel(
+  string type, string path, string branch, string kind, string model
+) {
+  // No deprecation adapter for barrier models, they were not around back then.
+  exists(QlBuiltins::ExtensionId madId |
+    Extensions::barrierGuardModel(type, path, branch, kind, madId) and
+    model = "MaD:" + madId.toString()
+  )
+}
+
 /** Holds if a summary model `row` exists for the given parameters. */
 private predicate summaryModel(
   string type, string path, string input, string output, string kind, string model
@@ -400,6 +420,8 @@ predicate isRelevantType(string type) {
   (
     sourceModel(type, _, _, _) or
     sinkModel(type, _, _, _) or
+    barrierModel(type, _, _, _) or
+    barrierGuardModel(type, _, _, _, _) or
     summaryModel(type, _, _, _, _, _) or
     typeModel(_, type, _)
   ) and
@@ -427,6 +449,8 @@ predicate isRelevantFullPath(string type, string path) {
   (
     sourceModel(type, path, _, _) or
     sinkModel(type, path, _, _) or
+    barrierModel(type, path, _, _) or
+    barrierGuardModel(type, path, _, _, _) or
     summaryModel(type, path, _, _, _, _) or
     typeModel(_, type, path)
   )
@@ -745,6 +769,32 @@ module ModelOutput {
       )
     }
 
+    /**
+     * Holds if a barrier model contributed `barrier` with the given `kind`.
+     */
+    cached
+    API::Node getABarrierNode(string kind, string model) {
+      exists(string type, string path |
+        barrierModel(type, path, kind, model) and
+        result = getNodeFromPath(type, path)
+      )
+    }
+
+    /**
+     * Holds if a barrier model contributed `barrier` with the given `kind`.
+     */
+    cached
+    API::Node getABarrierGuardNode(string kind, boolean branch, string model) {
+      exists(string type, string path, string branch_str |
+        branch = true and branch_str = "true"
+        or
+        branch = false and branch_str = "false"
+      |
+        barrierGuardModel(type, path, branch_str, kind, model) and
+        result = getNodeFromPath(type, path)
+      )
+    }
+
     /**
      * Holds if a relevant summary exists for these parameters.
      */
@@ -787,15 +837,27 @@ module ModelOutput {
   private import codeql.mad.ModelValidation as SharedModelVal
 
   /**
-   * Holds if a CSV source model contributed `source` with the given `kind`.
+   * Holds if an external model contributed `source` with the given `kind`.
    */
   API::Node getASourceNode(string kind) { result = getASourceNode(kind, _) }
 
   /**
-   * Holds if a CSV sink model contributed `sink` with the given `kind`.
+   * Holds if an external model contributed `sink` with the given `kind`.
    */
   API::Node getASinkNode(string kind) { result = getASinkNode(kind, _) }
 
+  /**
+   * Holds if an external model contributed `barrier` with the given `kind`.
+   */
+  API::Node getABarrierNode(string kind) { result = getABarrierNode(kind, _) }
+
+  /**
+   * Holds if an external model contributed `barrier-guard` with the given `kind` and `branch`.
+   */
+  API::Node getABarrierGuardNode(string kind, boolean branch) {
+    result = getABarrierGuardNode(kind, branch, _)
+  }
+
   private module KindValConfig implements SharedModelVal::KindValidationConfigSig {
     predicate summaryKind(string kind) { summaryModel(_, _, _, _, kind, _) }
 
diff --git a/ruby/ql/lib/codeql/ruby/frameworks/data/internal/ApiGraphModelsExtensions.qll b/ruby/ql/lib/codeql/ruby/frameworks/data/internal/ApiGraphModelsExtensions.qll
index 3f38c498f324..2a644aabb95d 100644
--- a/ruby/ql/lib/codeql/ruby/frameworks/data/internal/ApiGraphModelsExtensions.qll
+++ b/ruby/ql/lib/codeql/ruby/frameworks/data/internal/ApiGraphModelsExtensions.qll
@@ -20,6 +20,26 @@ extensible predicate sourceModel(
  */
 extensible predicate sinkModel(string type, string path, string kind, QlBuiltins::ExtensionId madId);
 
+/**
+ * Holds if the value at `(type, path)` should be seen as a barrier
+ * of the given `kind` and `madId` is the data extension row number.
+ */
+extensible predicate barrierModel(
+  string type, string path, string kind, QlBuiltins::ExtensionId madId
+);
+
+/**
+ * Holds if the value at `(type, path)` should be seen as a barrier guard
+ * of the given `kind` and `madId` is the data extension row number.
+ * `path` is assumed to lead to a parameter of a call (possibly `self`), and
+ * the call is guarding the parameter.
+ * `branch` is either `true` or `false`, indicating which branch of the guard
+ * is protecting the parameter.
+ */
+extensible predicate barrierGuardModel(
+  string type, string path, string branch, string kind, QlBuiltins::ExtensionId madId
+);
+
 /**
  * Holds if in calls to `(type, path)`, the value referred to by `input`
  * can flow to the value referred to by `output` and `madId` is the data
diff --git a/ruby/ql/lib/codeql/ruby/frameworks/data/internal/empty.model.yml b/ruby/ql/lib/codeql/ruby/frameworks/data/internal/empty.model.yml
index b887eed7c1c5..ec68e8fcb380 100644
--- a/ruby/ql/lib/codeql/ruby/frameworks/data/internal/empty.model.yml
+++ b/ruby/ql/lib/codeql/ruby/frameworks/data/internal/empty.model.yml
@@ -16,6 +16,16 @@ extensions:
       extensible: summaryModel
     data: []
 
+  - addsTo:
+      pack: codeql/ruby-all
+      extensible: barrierModel
+    data: []
+
+  - addsTo:
+      pack: codeql/ruby-all
+      extensible: barrierGuardModel
+    data: []
+
   - addsTo:
       pack: codeql/ruby-all
       extensible: neutralModel
diff --git a/shared/dataflow/codeql/dataflow/internal/FlowSummaryImpl.qll b/shared/dataflow/codeql/dataflow/internal/FlowSummaryImpl.qll
index 6cc9d6f88a45..4ab2eb1650c6 100644
--- a/shared/dataflow/codeql/dataflow/internal/FlowSummaryImpl.qll
+++ b/shared/dataflow/codeql/dataflow/internal/FlowSummaryImpl.qll
@@ -215,6 +215,35 @@ module Make<
         ]
     }
 
+    class AcceptingValue extends string {
+      AcceptingValue() {
+        this =
+          [
+            "true",
+            "false",
+            "no-exception",
+            "zero",
+            "not-zero",
+            "null",
+            "not-null",
+          ]
+      }
+
+      predicate isTrue() { this = "true" }
+
+      predicate isFalse() { this = "false" }
+
+      predicate isNoException() { this = "no-exception" }
+
+      predicate isZero() { this = "zero" }
+
+      predicate isNotZero() { this = "not-zero" }
+
+      predicate isNull() { this = "null" }
+
+      predicate isNotNull() { this = "not-null" }
+    }
+
     /**
      * A class used to represent provenance values for MaD models.
      *
@@ -2015,6 +2044,12 @@ module Make<
         not exists(interpretComponent(c))
       }
 
+      /** Holds if `acceptingvalue` is not a valid barrier guard accepting-value. */
+      bindingset[acceptingvalue]
+      predicate invalidAcceptingValue(string acceptingvalue) {
+        not acceptingvalue instanceof AcceptingValue
+      }
+
       /** Holds if `provenance` is not a valid provenance value. */
       bindingset[provenance]
       predicate invalidProvenance(string provenance) { not provenance instanceof Provenance }
@@ -2052,6 +2087,23 @@ module Make<
           Element n, string input, string kind, Provenance provenance, string model
         );
 
+        /**
+         * Holds if an external barrier specification exists for `n` with output specification
+         * `output` and kind `kind`.
+         */
+        predicate barrierElement(
+          Element n, string output, string kind, Provenance provenance, string model
+        );
+
+        /**
+         * Holds if an external barrier guard specification exists for `n` with input
+         * specification `input`, accepting value `acceptingvalue`, and kind `kind`.
+         */
+        predicate barrierGuardElement(
+          Element n, string input, AcceptingValue acceptingvalue, string kind,
+          Provenance provenance, string model
+        );
+
         class SourceOrSinkElement extends Element;
 
         /** An entity used to interpret a source/sink specification. */
@@ -2105,7 +2157,9 @@ module Make<
 
         private predicate sourceSinkSpec(string spec) {
           sourceElement(_, spec, _, _, _) or
-          sinkElement(_, spec, _, _, _)
+          sinkElement(_, spec, _, _, _) or
+          barrierElement(_, spec, _, _, _) or
+          barrierGuardElement(_, spec, _, _, _, _)
         }
 
         private module AccessPath = AccessPathSyntax::AccessPath<sourceSinkSpec/1>;
@@ -2160,11 +2214,34 @@ module Make<
           )
         }
 
+        private predicate barrierElementRef(
+          InterpretNode ref, SourceSinkAccessPath output, string kind, string model
+        ) {
+          exists(SourceOrSinkElement e |
+            barrierElement(e, output, kind, _, model) and
+            if outputNeedsReferenceExt(output.getToken(0))
+            then e = ref.getCallTarget()
+            else e = ref.asElement()
+          )
+        }
+
+        private predicate barrierGuardElementRef(
+          InterpretNode ref, SourceSinkAccessPath input, AcceptingValue acceptingvalue, string kind,
+          string model
+        ) {
+          exists(SourceOrSinkElement e |
+            barrierGuardElement(e, input, acceptingvalue, kind, _, model) and
+            if inputNeedsReferenceExt(input.getToken(0))
+            then e = ref.getCallTarget()
+            else e = ref.asElement()
+          )
+        }
+
         /** Holds if the first `n` tokens of `output` resolve to the given interpretation. */
         private predicate interpretOutput(
           SourceSinkAccessPath output, int n, InterpretNode ref, InterpretNode node
         ) {
-          sourceElementRef(ref, output, _, _) and
+          (sourceElementRef(ref, output, _, _) or barrierElementRef(ref, output, _, _)) and
           n = 0 and
           (
             if output = ""
@@ -2220,7 +2297,7 @@ module Make<
         private predicate interpretInput(
           SourceSinkAccessPath input, int n, InterpretNode ref, InterpretNode node
         ) {
-          sinkElementRef(ref, input, _, _) and
+          (sinkElementRef(ref, input, _, _) or barrierGuardElementRef(ref, input, _, _, _)) and
           n = 0 and
           (
             if input = ""
@@ -2280,6 +2357,30 @@ module Make<
           )
         }
 
+        /**
+         * Holds if `node` is specified as a barrier with the given kind in a MaD flow
+         * model.
+         */
+        predicate isBarrierNode(InterpretNode node, string kind, string model) {
+          exists(InterpretNode ref, SourceSinkAccessPath output |
+            barrierElementRef(ref, output, kind, model) and
+            interpretOutput(output, output.getNumToken(), ref, node)
+          )
+        }
+
+        /**
+         * Holds if `node` is specified as a barrier guard argument with the
+         * given kind in a MaD flow model.
+         */
+        predicate isBarrierGuardNode(
+          InterpretNode node, AcceptingValue acceptingvalue, string kind, string model
+        ) {
+          exists(InterpretNode ref, SourceSinkAccessPath input |
+            barrierGuardElementRef(ref, input, acceptingvalue, kind, model) and
+            interpretInput(input, input.getNumToken(), ref, node)
+          )
+        }
+
         final private class SourceOrSinkElementFinal = SourceOrSinkElement;
 
         signature predicate sourceOrSinkElementSig(
diff --git a/shared/mad/codeql/mad/ModelValidation.qll b/shared/mad/codeql/mad/ModelValidation.qll
index 5d4698bed1d4..9791355d03ae 100644
--- a/shared/mad/codeql/mad/ModelValidation.qll
+++ b/shared/mad/codeql/mad/ModelValidation.qll
@@ -173,7 +173,7 @@ module KindValidation<KindValidationConfigSig Config> {
     or
     exists(string kind, string msg | Config::sinkKind(kind) |
       not kind instanceof ValidSinkKind and
-      msg = "Invalid kind \"" + kind + "\" in sink model." and
+      msg = "Invalid kind \"" + kind + "\" in sink or barrier model." and
       // The part of this message that refers to outdated sink kinds can be deleted after June 1st, 2024.
       if kind instanceof OutdatedSinkKind
       then result = msg + " " + kind.(OutdatedSinkKind).outdatedMessage()
diff --git a/swift/ql/lib/codeql/swift/dataflow/internal/FlowSummaryImpl.qll b/swift/ql/lib/codeql/swift/dataflow/internal/FlowSummaryImpl.qll
index 46e2e63f2cab..692e3626080d 100644
--- a/swift/ql/lib/codeql/swift/dataflow/internal/FlowSummaryImpl.qll
+++ b/swift/ql/lib/codeql/swift/dataflow/internal/FlowSummaryImpl.qll
@@ -159,6 +159,19 @@ module SourceSinkInterpretationInput implements
     )
   }
 
+  predicate barrierElement(
+    Element n, string output, string kind, Public::Provenance provenance, string model
+  ) {
+    none()
+  }
+
+  predicate barrierGuardElement(
+    Element n, string input, Public::AcceptingValue acceptingvalue, string kind,
+    Public::Provenance provenance, string model
+  ) {
+    none()
+  }
+
   private newtype TInterpretNode =
     TElement_(Element n) or
     TNode_(Node n) or