CVE-2026-57817: Apache CXF: The authorization code hash (c_hash) is not enforced for the hybrid OIDC flow

[Colm O hEigeartaigh <coheigea () apache org>]

Severity: low 

Affected versions:

- Apache CXF (org.apache.cxf:cxf-rt-rs-security-sso-oidc) 4.2.0 before 4.2.3
- Apache CXF (org.apache.cxf:cxf-rt-rs-security-sso-oidc) 4.0.0 before 4.1.8
- Apache CXF (org.apache.cxf:cxf-rt-rs-security-sso-oidc) before 3.6.12

Description:

The OpenID Connect Core 1.0 specification mandates that the RP MUST validate the `c_hash` parameter when operating in 
the Hybrid Flow. If an Apache CXF RP is integrated with a non-compliant or misconfigured Identity Provider (IdP) that 
omits the `c_hash`, the RP becomes vulnerable to Authorization Code Substitution/Injection attacks. Users are 
recommended to upgrade to versions 4.2.3 or 4.1.8 or 3.6.12, which fix this issue.

Credit:

Guanping Zhang reported this vulnerability. (finder)

References:

https://cxf.apache.org/
https://www.cve.org/CVERecord?id=CVE-2026-57817