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Advisory record · GHSA-752w-5fwx-jx9f

PyJWT accepts unknown `crit` header extensions

CVSS 7.5 HighEPSS 0.0030 · 22nd percentile

Published by the GitHub Advisory Database at 13 Mar 2026, 20:05 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
pyjwtPyPI<2.12.02.12.0
Identifiers
GHSA-752w-5fwx-jx9f · CVE-2026-32597 · PYSEC-2026-120
Weakness (CWE)
CWE-345 · CWE-347 · CWE-863
Tags
Published
13 Mar 2026
Updated
10 Sept 2026

Machine-written summary

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

PyJWT versions before 2.12.0 do not validate the "crit" header parameter in JWS tokens, so they accept tokens that list extensions the library does not understand, which RFC 7515 says must be rejected. The source does not describe the attacker's requirements in detail, but an attacker who can supply such a token could bypass enforcement that relies on the critical extension, such as MFA or token binding checks. Upgrade to PyJWT 2.12.0 or later.

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
7.5 High 3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0030, the 22nd percentile, on 11 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:11 UTC First seen by agentprime
  2. 31 Oct 2026, 14:11 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.