CVE-2026-44898
Description
Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, render_toc_ul() builds a table-of-contents tree from a list of (level, id, text) tuples. Both the id value (used as href="#") and the text value (used as the visible link label) are inserted into 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 blocks directly into the rendered TOC. This vulnerability is fixed in 3.2.1.
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Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
mistunePyPI | >= 3.2.0, < 3.2.1 | 3.2.1 |
Affected products
1Patches
Vulnerability mechanics
References
5- github.com/lepture/mistune/security/advisories/GHSA-6269-cqxg-mhhvnvdExploitVendor AdvisoryWEB
- github.com/advisories/GHSA-6269-cqxg-mhhvghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-44898ghsaADVISORY
- github.com/lepture/mistune/commit/04880a0ghsaWEB
- github.com/lepture/mistune/releases/tag/v3.2.1nvdProductRelease NotesWEB
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