Description
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.
References
- www.cve.org/CVERecord ↗
- nvd.nist.gov/vuln/detail/CVE-2026-120459 ↗
- github.com/mpdavis/python-jose/blob/3.5.0/jose/backends/cryptography_backend.py ↗
- github.com/mpdavis/python-jose/blob/3.5.0/jose/backends/native.py ↗
- github.com/mpdavis/python-jose/issues/398 ↗
- www.vulncheck.com/advisories/python-jose-through-3.5.0-authentication-bypass-via-empty-hmac-key ↗
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This product uses the NVD API but is not endorsed or certified by the NVD. CVSS scores do not establish exploitation.