CVE-2026-85394CWE-347

CVE-2026-85394

Critical · published September 3, 2026

CVSS v3.1
9.1
EPSS
0%
Percentile
12.1
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
9.1 · CRITICAL
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CVSS v4.0
9.3 · 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
EPSS
0.00222 · 12.1th percentile
Weakness
CWE-347 · Improper Verification of Cryptographic Signature
Published
2026-09-03T23:17Z
References (6)
https://github.com/advisories/GHSA-6c5p-j8vq-pqhj · [email protected]https://github.com/mpdavis/python-jose · [email protected]https://github.com/mpdavis/python-jose/blob/018b310ddb8b50dcfd09a0c152117835a21dd656/jose/backends/native.py · [email protected]https://github.com/mpdavis/python-jose/blob/018b310ddb8b50dcfd09a0c152117835a21dd656/jose/utils.py · [email protected]https://github.com/mpdavis/python-jose/issues/414 · [email protected]https://www.vulncheck.com/advisories/python-jose-through-3.5.0-algorithm-confusion-via-der-encoded-public-key-as-hmac-secret · [email protected]
EPSS history
Timeline
  • 05 SEP 03:44Z
    EPSS moved — → 0%
    epss
  • 03 SEP 18:54Z
    python-jose through 3.5.0 Algorithm Confusion via DER-encoded Public Key as HMAC Secret
    cvelistv5