---
id: CVE-2026-59930
aliases:
  - PYSEC-2026-2218
  - GHSA-2hm2-hc3v-44h9
title: >-
  Mistune is a Python Markdown parser with renderers and plugins. Prior to
  3.3.0, the toc plugin and TableOfContents directive generate hea…
summary: >-
  Mistune is a Python Markdown parser with renderers and plugins. Prior to
  3.3.0, the toc plugin and TableOfContents directive generate heading IDs as
  predictable toc_N values without slugifying the heading text, allowing
  attacker-controll…
severity: medium
cvss: 4.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N'
vendor: mistune
product: mistune
ecosystem: pip
affected:
  - mistune < 3.3.0
patched:
  - mistune 3.3.0
published: '2026-07-08'
updated: '2026-07-13'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/PYSEC-2026-2218'
references:
  - url: 'https://github.com/lepture/mistune/releases/tag/v3.3.0'
  - url: >-
      https://github.com/lepture/mistune/commit/c4093c4742ed0d10d9332fb8edb455869b7b581b
  - url: 'https://github.com/lepture/mistune/security/advisories/GHSA-2hm2-hc3v-44h9'
tags:
  - osv
  - pip
epss: 0.00192
epssPercentile: 0.07798
ingestedAt: '2026-07-13T18:58:08.256Z'
---

## Overview

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, the toc plugin and TableOfContents directive generate heading IDs as predictable toc_N values without slugifying the heading text, allowing attacker-controlled id="toc_N" content to collide with generated anchors and redirect same-page navigation, CSS selectors, or JavaScript handlers. This issue is fixed in version 3.3.0.

## Affected packages

- `mistune < 3.3.0`

## Remediation

Upgrade to a patched release:

- `mistune 3.3.0`