Description

Improper verification of cryptographic signature vulnerability in Apache Syncope. When SRA is configured for OAuth 2.0 without JWKS set URI assigned, an attacker can forge arbitrary JWTs to impersonate any user identity and permissions, gaining full access to services proxied by SRA. This issue affects Apache Syncope: from 3.0.0-M0 through 3.0.16, from 4.0.0-M0 through 4.0.7, from 4.1.0-M0 through 4.1.2. Users are recommended to upgrade to version 4.0.8 / 4.1.3, which fix this issue.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.1",
  "pubDate": "2026-09-14T11:17:05.620Z",
  "pubdate": "2026-09-14T11:17:05.620Z",
  "executiveSummary": "An improper verification of cryptographic signature vulnerability has been identified within the Apache Syncope Secure Routing Agent (SRA) when configured for OAuth 2.0 authentication.\nThe vulnerability occurs specifically when a JSON Web Key Set (JWKS) URI is not explicitly defined in the SRA configuration.\nThis flaw allows an unauthenticated remote attacker to craft and forge arbitrary JSON Web Tokens (JWTs), effectively bypassing cryptographic validation mechanisms.\nSuccessful exploitation enables full impersonation of any user identity and their associated permissions, granting unauthorized administrative or standard access to any services proxied by the SRA.\nThe vulnerability affects Apache Syncope versions 3.0.0-M0 through 3.0.16, 4.0.0-M0 through 4.0.7, and 4.1.0-M0 through 4.1.2.\nGiven the ability to manipulate identity claims and elevate privileges, this vulnerability carries a critical risk profile for environments relying on SRA for perimeter security and service orchestration.",
  "technicalDetails": "The vulnerability originates in the Apache Syncope SRA component's handling of OAuth 2.0 token validation logic. When the SRA is deployed in an environment utilizing OAuth 2.0 for access control, the system expects a robust verification process for incoming JWTs. This process typically requires the verification of the token's cryptographic signature against a trusted public key retrieved from a JWKS URI.\nThe root cause is a flaw in the validation chain where the SRA fails to enforce mandatory signature verification in the absence of a configured JWKS URI. Instead of rejecting the authentication request or defaulting to a secure 'deny-all' state when the key source is undefined, the application logic proceeds to accept the token without verifying the integrity or origin of the cryptographic signature.\nAn attacker can exploit this by generating a malformed or arbitrary JWT. Since the SRA does not perform the necessary cryptographic check, the attacker can supply a token with manipulated claims—such as 'sub' (subject) for identity spoofing and custom roles or permissions—without needing the corresponding private key to sign the token. The SRA will parse these claims and establish a session based on the forged data.\nThe attack flow is as follows: 1) The attacker targets an SRA-proxied service; 2) The attacker crafts a JWT containing arbitrary claims representing an elevated or target user identity; 3) The attacker presents this forged JWT to the SRA; 4) The SRA, lacking a configured JWKS URI, fails to perform the signature validation step, treating the forged token as a valid, verified credential; 5) The SRA proxies the request to the backend service with the attacker's spoofed identity credentials.\nThis vulnerability is restricted to environments where the SRA is specifically configured for OAuth 2.0 without a defined JWKS URI. It allows an attacker to bypass authentication entirely, requiring no prior credentials or existing session state. The post-exploitation impact is severe, as the attacker achieves full identity impersonation, effectively gaining the rights of the targeted user account across all downstream services protected by the SRA, potentially leading to total system compromise."
}