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Advisory record · GHSA-pxh4-856f-4h89

PyJWT: HS256/384/512 verify accepts empty HMAC key via oct JWK (PyJWK/PyJWKClient) enabling token forgery

CVSS 7.4 High

Published by the GitHub Advisory Database at 22 Oct 2026, 15:48 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
pyjwtPyPI<2.14.02.14.0
Identifiers
GHSA-pxh4-856f-4h89
Weakness (CWE)
CWE-347
Tags
Published
22 Oct 2026
Updated
22 Oct 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

PyJWT versions before 2.14.0 accept an HMAC key of zero length when it is loaded from a symmetric (kty=oct) JWK with an empty k value, through the PyJWK, PyJWKSet and PyJWKClient verification path. An unauthenticated attacker can forge tokens with arbitrary claims that verify successfully when the application's signing secret is unset. Upgrade to PyJWT 2.14.0, which fixes the issue.

Written 1 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
7.4 High 3.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N GitHub Advisory Database
  • CISA KEV Not listed.
  • EPSS No score.

Timeline

  1. 31 Oct 2026, 14:08 UTC First seen by agentprime
  2. 31 Oct 2026, 14:08 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.