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High severity7.4NVD Advisory· Published Sep 28, 2026· Updated Oct 7, 2026

CVE-2026-102266

CVE-2026-102266

Description

PyJWT is a Python implementation of JSON Web Token standards. From 2.13.0 until 2.14.0, HMACAlgorithm.from_jwk is affected because PyJWK verification path used the decoded key without applying prepare_key validation. This occurs when a trusted JWK Set contains an oct entry with an empty k value. As a result, an attacker signs an HMAC token with the same zero-length key accepted by PyJWT. Consequently, forged token can carry arbitrary authenticated claims. This issue is fixed in version 2.14.0.

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Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
PyJWTPyPI
>= 2.13.0, < 2.14.02.14.0

Affected products

59

Patches

Vulnerability mechanics

References

5

News mentions

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