Cross-site Scripting (XSS) Affecting mistune package, versions *


Severity

Recommended
low

Based on Debian security rating.

Threat Intelligence

EPSS
0.23% (14th percentile)

Do your applications use this vulnerable package?

In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.

Test your applications
  • Snyk IDSNYK-DEBIAN11-MISTUNE-17099690
  • published30 May 2026
  • disclosed26 May 2026

Introduced: 26 May 2026

CVE-2026-44898  (opens in a new tab)
CWE-79  (opens in a new tab)

How to fix?

There is no fixed version for Debian:11 mistune.

NVD Description

Note: Versions mentioned in the description apply only to the upstream mistune package and not the mistune package as distributed by Debian. See How to fix? for Debian:11 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1