CVE-2026-44897
Medium
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.
SeverityMedium
CVSS6.1
Exploit probability—
ProductMistune
PublishedMay 26, 2026
First seenMay 26, 2026
Weakness typeCWE-79Cross-site scripting (XSS)
How to fix
Update
- mistune_project mistune3.2.1 or later
- mistune3.2.1 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mistune_project mistune | v < 3.2.1 | 3.2.1 |
| mistunePyPI | v < 3.2.1 | 3.2.1 |
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