CVE-2026-44898
Severity CVSS v4.0:
Pending analysis
Type:
CWE-79
Cross-Site Scripting (XSS)
Publication date:
26/05/2026
Last modified:
26/05/2026
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.
Impact
Base Score 3.x
6.10
Severity 3.x
MEDIUM