CVE-2026-120459
python-jose through 3.5.0 Authentication Bypass via Empty HMAC Key
CVSS Score
7.4
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-347 |
| Vendor | mpdavis |
| Product | python-jose |
| Published | Nov 2, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None
Affected Versions
mpdavis / python-jose
0 ≤ 3.5.0
References
github.com: https://github.com/mpdavis/python-jose/issues/398 github.com: https://github.com/mpdavis/python-jose/blob/3.5.0/jose/backends/native.py github.com: https://github.com/mpdavis/python-jose/blob/3.5.0/jose/backends/cryptography_backend.py vulncheck.com: https://www.vulncheck.com/advisories/python-jose-through-3.5.0-authentication-bypass-via-empty-hmac-key
Credits
Gavin Blacklock Conner Webber