CVE-2026-85394 Details
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.
A vulnerability exists in python-jose versions through 3.5.0, where the library improperly validates asymmetric keys during HMAC initialization. It accepts DER-encoded public keys that lack PEM armor or SSH prefixes. This flaw allows attackers with access to the service's public key to forge HS256 tokens that bypass verification, particularly when algorithm restrictions are not explicitly applied. This issue stems from an incomplete fix for a previous vulnerability, CVE-2024-33663.
Users can upgrade to python-jose version 3.5.0 or later, where this vulnerability has been addressed.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Sep 3, 2026CISA-ADP
Assessed Sep 14, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/advisories/GHSA-6c5p-j8vq-pqhj | [email protected] | AdvisoryNot ApplicableVendor |
| https://github.com/mpdavis/python-jose | [email protected] | Vendor |
| https://github.com/mpdavis/python-jose/blob/018b310ddb8b50dcfd09a0c152117835a21dd656/jose/backends/native.py | [email protected] | Source CodeVendor |
| https://github.com/mpdavis/python-jose/blob/018b310ddb8b50dcfd09a0c152117835a21dd656/jose/utils.py | [email protected] | Source CodeVendor |
| https://github.com/mpdavis/python-jose/issues/414 | [email protected] | ExploitIssue TrackingTechnical DescriptionVendor |
| https://www.vulncheck.com/advisories/python-jose-through-3.5.0-algorithm-confusion-via-der-encoded-public-key-as-hmac-secret | [email protected] | AdvisoryTechnical Description |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-347 | Improper Verification of Cryptographic Signature | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| python-jose | <= 3.5.0 (semver) |
CPE
Remediation
| |
Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 14, 2026 | CVE Modified | CISA-ADP |
| Sep 3, 2026 | New CVE Received | [email protected] |