python-jose through 3.5.0 Authentication Bypass via Empty HMAC Key

Summary

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.

Remediation

1. Inventory every mpdavis python-jose deployment, including staging.
2. No fixed version appears in the public sources yet. Check the references below and the vendor directly.

References

• Advisoryhttps://www.vulncheck.com/advisories/python-jose-through-3.5.0-authentication-bypass-via-empty-hmac-key
• Referencehttps://github.com/mpdavis/python-jose/blob/3.5.0/jose/backends/cryptography_backend.py
• Referencehttps://github.com/mpdavis/python-jose/blob/3.5.0/jose/backends/native.py
• Referencehttps://github.com/mpdavis/python-jose/issues/398