CVE-2026-85394

python-jose through 3.5.0 Algorithm Confusion via DER-encoded Public Key as HMAC Secret

Published Sep 3, 2026 CVSS 4.0 · 9.3 Critical EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-3qf3-8w2g-rqmx python-jose algorithm confusion guard bypassed by DER-encoded public keys
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Mpdavis
Mpdavis python-jose
Vendors & Products Mpdavis
Mpdavis python-jose
Type Values Removed Values Added
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.
Title python-jose through 3.5.0 Algorithm Confusion via DER-encoded Public Key as HMAC Secret
First Time appeared Python-jose Project
Python-jose Project python-jose
Weaknesses CWE-347
CPEs cpe:2.3:a:python-jose_project:python-jose:*:*:*:*:*:*:*:*
Vendors & Products Python-jose Project
Python-jose Project python-jose
References
Metrics cvssV3_1

{'score': 9.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'}

cvssV4_0

{'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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
VulnCheck
Published
Updated
Sep 14, 2026, 1:50 PM
Reserved
Sep 3, 2026, 6:10 PM
Status
Deferred
Published
Sep 3, 2026, 7:17 PM
Modified
Sep 24, 2026, 8:43 PM