Impact

AttachmentUploadServlet also saves user controlled data (request.getInputStream()) to a user specified location (request.getHeader("File-Name")):

String fileName = URLDecoder.decode(request.getHeader("File-Name"), StandardCharsets.UTF_8.name());
...
String attachmentName = attachmentSuppport.saveAttachment(fileName, request.getInputStream());

This file system operation occurs before any authentication or authorization checks are enforced.

This issue may lead to arbitrary file upload which can be used to upload a WebShell to OneDev server

Patches

This issue is addressed in 4.0.3 by only allowing uploaded file to be in attachments folder. The webshell issue is not possible as OneDev never executes files in attachments folder.

Credits

This issue was discovered by @pwntester