CVE-2026-63687: Apache Cxf

Critical severity, CVSS 9.1. EPSS: 0.3% chance of exploitation in the next 30 days.

Apache CXF's JwtRequestCodeFilter copies all claims from a signed request JWT into the authorization parameter map without excluding security-sensitive parameters. A client that can produce a validly-signed request JWT (e.g., one whose client_secret is known or compromised) can thereby substitute the code_challenge, code_challenge_method, nonce, and state values that were set in the outer HTTP request, undermining PKCE integrity and OpenID Connect replay protection. Users are recommended to upgrade to versions 4.2.3 or 4.1.8 or 3.6.12, which fix this issue.

Affected products

• Apache Cxf: before 3.6.12 (fixed in 3.6.12); from 4.0.0, before 4.1.8 (fixed in 4.1.8); from 4.2.0, before 4.2.3 (fixed in 4.2.3)

Published 2026-08-06. Last modified 2026-08-07.