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.

Project Subscriptions

Vendors Products
Lepture Subscribe
Mistune Subscribe
Mistune Project Subscribe
Mistune Subscribe
Advisories
Source ID Title
Github GHSA Github GHSA GHSA-ccfx-mfmx-2fx9 Mistune Image Directive CSS Injection Vulnerability
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Thu, 28 May 2026 13:45:00 +0000

Type Values Removed Values Added
First Time appeared Mistune Project
Mistune Project mistune
CPEs cpe:2.3:a:mistune_project:mistune:*:*:*:*:*:*:*:*
Vendors & Products Mistune Project
Mistune Project mistune

Wed, 27 May 2026 15:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Tue, 26 May 2026 23:00:00 +0000

Type Values Removed Values Added
First Time appeared Lepture
Lepture mistune
Vendors & Products Lepture
Lepture mistune

Tue, 26 May 2026 21:15:00 +0000

Type Values Removed Values Added
Description 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.
Title Mistune Image Directive CSS Injection Vulnerability
Weaknesses CWE-79
References
Metrics cvssV3_1

{'score': 4.7, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N'}


Projects

Sign in to view the affected projects.

cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-05-27T13:31:02.744Z

Reserved: 2026-05-07T21:50:33.546Z

Link: CVE-2026-44899

cve-icon Vulnrichment

Updated: 2026-05-27T13:28:52.303Z

cve-icon NVD

Status : Analyzed

Published: 2026-05-26T21:16:39.953

Modified: 2026-05-28T13:38:38.980

Link: CVE-2026-44899

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-05-26T23:15:20Z

Weaknesses