CVE-2026-44899

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.

• CWE-79

• https://github.com/lepture/mistune/releases/tag/v3.2.1Product, Release Notes
• https://github.com/lepture/mistune/security/advisories/GHSA-ccfx-mfmx-2fx9Exploit, Vendor Advisory
• https://github.com/lepture/mistune/security/advisories/GHSA-ccfx-mfmx-2fx9Exploit, Vendor Advisory

Published

May 26, 2026

Last Modified

Jul 24, 2026

Status

Analyzed

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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