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Advisory record · GHSA-ffc3-869f-jxw9

PyJWT: Asymmetric-PEM detection bypass: whitespace/line-ending-mutated public keys skip the HS/asymmetric confusion guard

CVSS 9.1 CriticalCriticalEPSS 0.0024 · 14th percentile

Critical, because:

  • CVSS score 9.1: 9.0 or more.

How we decide what’s critical

Published by the GitHub Advisory Database at 29 Sept 2026, 23:17 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-ffc3-869f-jxw9 · CVE-2026-102268 · PYSEC-2026-4145
Weakness (CWE)
CWE-347
Tags
Published
29 Sept 2026
Updated
1 Oct 2026

Machine-written summary

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

PyJWT (PyPI package pyjwt) versions before 2.14.0 are affected. When a jwt.decode allow-list mixes an HMAC algorithm with an asymmetric one, and the verification key is raw PEM text in a form that cryptography accepts but PyJWT's PEM detection misses, an attacker who holds the public key can forge HS256 tokens that verify. Upgrade to pyjwt 2.14.0, which contains the fix. Alternatively, use only asymmetric algorithms in the allow-list or verify with PyJWK objects.

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
9.1 Critical 3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0024, the 14th percentile, on 7 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:09 UTC First seen by agentprime
  2. 31 Oct 2026, 14:09 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.