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Medium severity5.4NVD Advisory· Published May 28, 2026· Updated Jun 1, 2026

CVE-2026-48523

CVE-2026-48523

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.

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Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
pyjwtPyPI
>= 2.9.0, < 2.13.02.13.0

Affected products

56

Patches

Vulnerability mechanics

References

4

News mentions

0

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