CVE-2026-48523Medium· 5.4▾ SunlitPyJWT is a JSON Web Token implementation in Python. From 2.9.0 to 2.12.1, there is a verifier-side algorithm allow-list bypass when jwt.decode() or jwt.decode_complete() are called with a PyJWK key. The token header alg is checked agains…
▾ Sunlit zone — Low / medium · no exploitation signal
impact 29.7 · likelihood 0 · exploitation 0
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Exploit-prediction probability, daily snapshots since Aug 2.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via NVD
0.1%
Last analysed / modified upstream
0.1% → 0.2%
PyJWT is a JSON Web Token implementation in Python. From 2.9.0 to 2.12.1, there is a verifier-side algorithm allow-list bypass when jwt.decode() or jwt.decode_complete() are called with a PyJWK key. The token header alg is checked against the caller-supplied algorithms allow-list, but signature verification is performed with the algorithm bound to the PyJWK object instead of the header algorithm. An attacker who controls a registered JWK/JWKS private key can sign with a disallowed algorithm, advertise an allowed algorithm in the JWT header, and still be accepted. The issue affects the documented PyJWKClient.get_signing_key_from_jwt(...) flow. This vulnerability is fixed in 2.13.0.
pyjwt >= 2.9.0, < 2.13.0Upgrade past the affected range:
pyjwt 2.13.0Affected packages:
pyjwt >= 2.9.0, < 2.13.0Patched in:
pyjwt 2.13.0Connected by shared product, vendor, weakness, or advisory.
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