CVE-2026-120459
python-jose through 3.5.0 Authentication Bypass via Empty HMAC Key
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.
Fixes and workarounds
No remediation reported in collected sources.
Missing remediation information is not evidence that no patch exists.
Affected products and versions
| Product | Versions | Authority |
|---|---|---|
| python-jose mpdavis python-jose
pypi |
≥ 0; ≤ 3.5.0 (affected, semver)
Other versions: unaffected |
CNA: VulnCheck |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 4.0 / 9.1 critical |
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 | CNA: VulnCheck |
| 3.1 / 7.4 high |
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N | CNA: VulnCheck |
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://github.com/mpdavis/python-jose/issues/398CNA: VulnCheck · issue-tracking
- https://github.com/mpdavis/python-jose/blob/3.5.0/jose/backends/native.pyCNA: VulnCheck · technical-description
- https://github.com/mpdavis/python-jose/blob/3.5.0/jose/backends/cryptography_backend.pyCNA: VulnCheck · technical-description
- https://www.vulncheck.com/advisories/python-jose-through-3.5.0-authentication-bypass-via-empty-hmac-keyCNA: VulnCheck · third-party-advisory
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