NVD security advisoryCritical
Critical advisory for python-jose
CVE-2026-120459 · Reported 2 Nov 2026
Full advisory details, affected packages, severity context, and original source.
Affected technology
python-josePython ecosystem
Advisory overview
python-jose through 3.5.0 contains an authentication bypass vulnerability that allows unauthenticated attackers to forge JWTs because HMACKey and CryptographyHMACKey accept zero-length HMAC secrets. When an application's HS256/HS384/HS512 verification key resolves to empty, such as an oct JWK with empty k, attackers can forge tokens with arbitrary claims that jwt.decode accepts.
Related references
- https://github.com/mpdavis/python-jose/blob/3.5.0/jose/backends/cryptography_backend.py
- https://github.com/mpdavis/python-jose/blob/3.5.0/jose/backends/native.py
- https://github.com/mpdavis/python-jose/issues/398
- https://www.vulncheck.com/advisories/python-jose-through-3.5.0-authentication-bypass-via-empty-hmac-key