CVE-2026-85394

critical

Description

python-jose through 3.5.0 fails to properly validate asymmetric keys in HMAC initialization, accepting DER-encoded public keys that lack PEM armor or SSH prefixes. Attackers holding the service's public key can forge HS256 tokens that pass verification when algorithms are not explicitly restricted. This is an incomplete fix for CVE-2024-33663.

References

https://www.vulncheck.com/advisories/python-jose-through-3.5.0-algorithm-confusion-via-der-encoded-public-key-as-hmac-secret

https://github.com/mpdavis/python-jose/issues/414

https://github.com/mpdavis/python-jose/blob/018b310ddb8b50dcfd09a0c152117835a21dd656/jose/utils.py

https://github.com/mpdavis/python-jose/blob/018b310ddb8b50dcfd09a0c152117835a21dd656/jose/backends/native.py

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

https://github.com/advisories/GHSA-6c5p-j8vq-pqhj

Details

Source: Mitre, NVD

Published: 2026-09-03

Updated: 2026-09-03

Risk Information

CVSS v2

Base Score: 9.4

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

Severity: High

CVSS v3

Base Score: 9.1

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

Severity: Critical

CVSS v4

Base Score: 9.3

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

Severity: Critical

EPSS

EPSS: 0.00222