CVE-2026-120459: critical vulnerability in mpdavis python-jose
python-jose through 3.5.0 Authentication Bypass via Empty HMAC Key
Published
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28Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 9.1epss 0.3%
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.
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
Affected products
mpdavis · python-joseRelated CVEs — mpdavis python-jose
In the same product, most dangerous first.
References
https://github.com/mpdavis/python-jose/blob/3.5.0/jose/backends/cryptography_backend.pyhttps://github.com/mpdavis/python-jose/blob/3.5.0/jose/backends/native.pyhttps://github.com/mpdavis/python-jose/issues/398https://www.vulncheck.com/advisories/python-jose-through-3.5.0-authentication-bypass-via-empty-hmac-key