CVE WatchOct 25, 2026

CVE-2026-48523

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.deco

CVSS

5.4

Medium

EPSS

0.1%

KEV

—

Exploit Today

0-100

Published: May 28, 2026 · Last modified: Oct 25, 2026 · CWE-347

EPSS · 30d

0.1%EPSS · 30 days0.2%

2026-09-272026-10-25

Technical description

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.

Official references

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