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6.1 Medium

CVE-2026-44898 Mistune is a Python Markdown parser with renderers and plugins

Description

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, render_toc_ul() builds a <ul> table-of-contents tree from a list of (level, id, text) tuples. Both the id value (used as href="#<id>") and the text value (used as the visible link label) are inserted into <a> tags via a plain Python format string — with no HTML escaping applied to either value. When heading IDs are derived from user-supplied heading text (the standard use-case for readable slug anchors), an attacker can craft a heading whose text breaks out of the href="#..." attribute context, injecting arbitrary HTML tags including <script> blocks directly into the rendered TOC. This vulnerability is fixed in 3.2.1.

Affected products and versions

Product Affected versions Fixed in
mistune 3.2 earliest → < 3.2.1 3.2.1

References

Timeline

  1. Published
  2. Last modified

Other CVEs of mistune

The 28 CVEs of mistune →
CVE-2026-121437 Mistune from 3.3.0 before 3.3.4 contains a denial of service vulnerability that allows remote attackers to exhaust CPU… 8.7 High CVE-2026-121438 Mistune before 3.3.3 contains a denial of service vulnerability in InlineParser.parse_link that allows attackers to… 6.9 Medium CVE-2026-115354 Mistune before 3.3.0 contains a path traversal vulnerability in the opt-in Include directive that allows attackers to… 7.1 High CVE-2026-115355 Mistune before 3.3.0 contains a path traversal vulnerability in the Include directive that allows attackers to read… 8.7 High
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