Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, HTMLRenderer.heading() builds the opening <hN> tag by string-concatenating the id attribute value directly into the HTML — with no call to escape(), safe_entity(), or any other sanitisation function. A double-quote character " in the id value terminates the attribute, allowing an attacker to inject arbitrary additional attributes (event handlers, src=, href=, etc.) into the heading element. This vulnerability is fixed in 3.2.1.
History

Mon, 01 Jun 2026 17:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


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

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, HTMLRenderer.heading() builds the opening <hN> tag by string-concatenating the id attribute value directly into the HTML — with no call to escape(), safe_entity(), or any other sanitisation function. A double-quote character " in the id value terminates the attribute, allowing an attacker to inject arbitrary additional attributes (event handlers, src=, href=, etc.) into the heading element. This vulnerability is fixed in 3.2.1.
Title Mistune Heading ID Attribute Injection XSS
Weaknesses CWE-79
References
Metrics cvssV3_1

{'score': 6.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published: 2026-05-26T20:40:42.290Z

Updated: 2026-06-01T17:09:12.432Z

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

Link: CVE-2026-44897

cve-icon Vulnrichment

Updated: 2026-06-01T17:09:07.878Z

cve-icon NVD

Status : Analyzed

Published: 2026-05-26T21:16:39.657

Modified: 2026-05-28T13:42:42.863

Link: CVE-2026-44897

cve-icon Redhat

No data.