CVE-2026-85394criticalCWE-347

CVE-2026-85394: critical vulnerability in mpdavis python-jose

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

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28Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 9.3epss 0.2%
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.
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
Affected products
mpdavis · python-jose
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