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


Severity

Recommended
low

Based on Debian security rating.

Threat Intelligence

EPSS
0.23% (14th percentile)

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  • Snyk IDSNYK-DEBIAN11-MISTUNE-17099040
  • published30 May 2026
  • disclosed26 May 2026

Introduced: 26 May 2026

CVE-2026-44899  (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, the Image directive plugin validates the :width: and :height: options with a regex compiled as _num_re = re.compile(r"^\d+(?:.\d*)?"). When the validated value is not a plain integer, render_block_image() inserts it directly into a style="width:...;" or style="height:...;" attribute. Because the value was accepted by the prefix-only regex, any CSS after the leading digits reaches the style= attribute verbatim and without escaping. This vulnerability is fixed in 3.2.1.

CVSS Base Scores

version 3.1