Authentication Bypass in Apache CXF OAuth2 TokenIntrospectionService

Compliance Impact

The vulnerability allows unauthenticated network attackers to access the OAuth2 TokenIntrospectionService endpoint if authentication is not enabled, potentially exposing sensitive token information.

Such unauthorized access could lead to unauthorized disclosure or misuse of authentication tokens, which may impact compliance with data protection standards and regulations like GDPR and HIPAA that require strict access controls and protection of sensitive data.

However, this vulnerability only applies if authentication is not enabled on the service, which is considered a misconfiguration. Properly enabling authentication and upgrading to fixed versions mitigates this risk.

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Executive Summary

CVE-2026-50623 is an authentication bypass vulnerability in the OAuth2 TokenIntrospectionService of Apache CXF. The issue is caused by a missing 'throw' keyword in the security context check, which allows unauthenticated network attackers to access the introspection endpoint located at /services/oauth2/introspect.

This vulnerability only affects users who have not enabled authentication on the service, meaning it acts as a safeguard in case authentication was forgotten or not configured.

Users are recommended to upgrade to Apache CXF versions 4.2.2 or 4.1.7, which contain fixes for this issue.

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Impact Analysis

If you are running an affected version of Apache CXF and have not enabled authentication on the OAuth2 TokenIntrospectionService, an unauthenticated attacker could access the introspection endpoint.

This could potentially allow unauthorized parties to gain information about OAuth2 tokens, which might lead to unauthorized access or misuse of protected resources.

However, if authentication is properly enabled on the service, this vulnerability does not pose a risk.

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Detection Guidance

This vulnerability allows unauthenticated access to the OAuth2 TokenIntrospectionService endpoint at /services/oauth2/introspect if authentication is not enabled.

To detect this vulnerability, you can attempt to access the introspection endpoint without authentication and observe if access is granted.

For example, you can use the following command to test access:

• curl -v http://<server-address>/services/oauth2/introspect

If the endpoint responds without requiring authentication, the system is vulnerable.

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Mitigation Strategies

The primary mitigation step is to upgrade Apache CXF to version 4.2.2 or 4.1.7, where this vulnerability is fixed.

Additionally, ensure that authentication is properly enabled on the OAuth2 TokenIntrospectionService endpoint to prevent unauthenticated access.

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