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Advisory record · GHSA-8wjv-2p76-3863

PyJWT: Uncaught RecursionError in jwt.decode() on deeply nested token header

CVSS 5.3 MediumEPSS 0.0034 · 28th percentile

Published by the GitHub Advisory Database at 29 Sept 2026, 23:43 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
pyjwtPyPI>=2.13.0, <2.14.02.14.0
Identifiers
GHSA-8wjv-2p76-3863 · CVE-2026-102265 · PYSEC-2026-4142
Weakness (CWE)
CWE-674
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 versions 2.13.0 up to but not including 2.14.0 are affected. When a JWT's header contains deeply nested JSON, jwt.decode() raises a RecursionError, which is not a PyJWTError, so applications that catch only PyJWT errors can fail with a server error. An unauthenticated attacker can trigger this with a single crafted unsigned token, causing repeated denial of service on token-validating endpoints. Upgrade to PyJWT 2.14.0, which translates this error into DecodeError.

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
5.3 Medium 3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0034, the 28th percentile, on 9 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.