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Envoy crashes when HTTP ext_proc processes local replies

Moderate severity GitHub Reviewed Published Mar 20, 2025 in envoyproxy/envoy • Updated Mar 21, 2025

Package

gomod github.com/envoyproxy/envoy (Go)

Affected versions

< 1.30.10
>= 1.31.0, < 1.31.6
>= 1.32.0, < 1.32.4
>= 1.33.0, < 1.33.1

Patched versions

1.30.10
1.31.6
1.32.4
1.33.1

Description

Summary

Envoy's ext_proc HTTP filter is at risk of crashing if a local reply is sent to the external server due to the filter's life time issue. A known situation is the fail of a websocket handshake will trigger a local reply leading to the crash of Envoy.

PoC

If both websocket and ext_proc are enabled, a failed handshake will trigger a local reply, thus ext_proc will crash.

Mitigation

  1. Disable websocket traffic
  2. Change the websocket response from backend to always return 101 Switch protocol based on RFC.
  3. Apply the patch and the ext_proc filter will not send the local reply that is generated by Envoy to the ext_proc server for processing.
  4. Apply the patch that the router will cancel the upstream requests when sending a local reply.

Impact

Denial of service

Reporter

Vasilios Syrakis
Fernando Cainelli

References

@phlax phlax published to envoyproxy/envoy Mar 20, 2025
Published by the National Vulnerability Database Mar 21, 2025
Published to the GitHub Advisory Database Mar 21, 2025
Reviewed Mar 21, 2025
Last updated Mar 21, 2025

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(24th percentile)

Weaknesses

CVE ID

CVE-2025-30157

GHSA ID

GHSA-cf3q-gqg7-3fm9

Source code

Credits

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