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Advisory record · GHSA-2hm2-hc3v-44h9

Mistune toc / TableOfContents directive: heading IDs use predictable `toc_N` numbering with no slugification, allowing collision with attacker-controlled `id="toc_N"` content

CVSS 4.3 MediumEPSS 0.0019 · 8th percentile

Published by the GitHub Advisory Database at 20 Jul 2026, 21:35 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-2hm2-hc3v-44h9 · CVE-2026-59930 · PYSEC-2026-2218
Weakness (CWE)
CWE-345 · CWE-1284
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 give table-of-contents headings predictable IDs like toc_1 and toc_2. An attacker who can inject raw HTML with id attributes can redirect same-page links and CSS or JavaScript aimed at those IDs. Upgrade to mistune 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
4.3 Medium 3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N CNA (GitHub_M)
  • CISA KEV Not listed.
  • EPSS 0.0019, the 8th percentile, on 7 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.