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Advisory record · GHSA-8mpj-m6qm-5qr8

Mistune directives/include: mutual `.. include::` recursion crashes the renderer with `RecursionError`, denial of service via two attacker-controlled markdown files

CVSS 5.3 MediumEPSS 0.0053 · 44th percentile

Published by the GitHub Advisory Database at 20 Jul 2026, 21:24 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
mistunePyPI<3.3.03.3.0
Identifiers
GHSA-8mpj-m6qm-5qr8 · CVE-2026-59927 · PYSEC-2026-2215
Weakness (CWE)
CWE-674 · CWE-755
Tags
Published
20 Jul 2026
Updated
20 Jul 2026

Machine-written summary

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

Mistune versions before 3.3.0 are vulnerable to a denial of service in the Include directive: two markdown files that include each other cause unbounded recursion until Python raises a RecursionError, which is not caught and propagates out of the renderer. An attacker who can supply or write two markdown files that the application renders can crash rendering on demand. Upgrade mistune to 3.3.0 or later.

Written 5 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 0.0053, the 44th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

  1. 31 Oct 2026, 14:42 UTC First seen by agentprime
  2. 31 Oct 2026, 14:42 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.