by Kastro
Paper/Archive/CVE-2026-120459

CVE-2026-120459

mpdavis python-jose — python-jose through 3.5.0 Authentication Bypass via Empty HMAC Key

CVSS 9.1
critical.is priorityof 100
27
CVSS 9.1 (CNA)9.1 / 10 × 3027.3Not in CISA KEV+300.0No EPSS score.000 × 200.0No public exploit+100.0SSVC exploitation: unknown+100.0
Description · from the CVE record

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.

Affected

ProductAffectedFixed inSource
python-jose≤ 3.5.0–CNA

Scores by source

VulnCheck (CNA)9.1CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
VulnCheck (CNA)7.4CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

References

refgithub.com/mpdavis/python-jose/issues/398writeupgithub.com/mpdavis/python-jose/blob/3.5.0/jose/backends/native.pywriteupgithub.com/mpdavis/python-jose/blob/3.5.0/jose/backends/cryptography_backend.pywriteupvulncheck.com/advisories/python-jose-through-3.5.0-authentication-bypass-via-empty-hmac-key