CVE-2026-50623: Apache CXF: Authentication Bypass in OAuth2 TokenIntrospectionService 

Severity: moderate 

Affected versions:

- Apache CXF (org.apache.cxf:cxf-rt-rs-security-oauth2) 4.2.0 before 4.2.2
- Apache CXF (org.apache.cxf:cxf-rt-rs-security-oauth2) 4.0.0 before 4.1.7
- Apache CXF (org.apache.cxf:cxf-rt-rs-security-oauth2) before 3.6.12

Description:

An authentication bypass vulnerability exists in the OAuth2 TokenIntrospectionService in Apache CXF. Due to a missing 'throw' keyword in the security context check, the introspection endpoint (/services/oauth2/introspect) can be accessed by any unauthenticated network attacker. However note that this is a safeguard only in the case that someone forgot to enable authentication on the service. Users are recommended to upgrade to version 4.2.2 or 4.1.7 or 3.6.12, which fixes this issue.

Credit:

Guanping Zhang reported this vulnerability. (finder)

References:

https://lists.apache.org/thread/ydzj8m5mqmjy13xgyj9mkk9hfff63qq7
https://cxf.apache.org/
https://www.cve.org/CVERecord?id=CVE-2026-50623