Vulnerability Description
LibJWT is a C JSON Web Token Library. From 3.0.0 to 3.3.2, libjwt accepts an RSA JWK that does not contain an alg parameter as the verification key for an HS256/HS384/HS512 token. In the OpenSSL backend, this causes HMAC verification to run with a zero-length key, so an attacker can forge a valid JWT without knowing any secret or RSA private key. This is an algorithm-confusion authentication bypass. It affects applications that load RSA keys from JWKS where alg is omitted, which is valid JWK syntax and common in real deployments, and then choose the verification algorithm from the JWT header, for example in a kid lookup callback. This vulnerability is fixed in 3.3.3.
Related Weaknesses (CWE)
References
- https://github.com/benmcollins/libjwt/security/advisories/GHSA-q843-6q5f-w55g
- https://github.com/benmcollins/libjwt/security/advisories/GHSA-q843-6q5f-w55g
FAQ
What is CVE-2026-44699?
CVE-2026-44699 is a documented vulnerability. LibJWT is a C JSON Web Token Library. From 3.0.0 to 3.3.2, libjwt accepts an RSA JWK that does not contain an alg parameter as the verification key for an HS256/HS384/HS512 token. In the OpenSSL backe...
How severe is CVE-2026-44699?
CVSS scoring is not yet available for CVE-2026-44699. Check NVD for updates.
Is there a patch for CVE-2026-44699?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.