CVE-2026-120459

critical

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

https://www.vulncheck.com/advisories/python-jose-through-3.5.0-authentication-bypass-via-empty-hmac-key

https://github.com/mpdavis/python-jose/issues/398

https://github.com/mpdavis/python-jose/blob/3.5.0/jose/backends/native.py

https://github.com/mpdavis/python-jose/blob/3.5.0/jose/backends/cryptography_backend.py

https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-115219

Details

Source: Mitre, NVD

Published: 2026-11-02

Updated: 2026-11-02

Risk Information

CVSS v2

Base Score: 7.1

Vector: CVSS2#AV:N/AC:H/Au:N/C:C/I:C/A:N

Severity: High

CVSS v3

Base Score: 7.4

Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Severity: High

CVSS v4

Base Score: 9.1

Vector: 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

Severity: Critical

EPSS

EPSS: 0.00251