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6.1 Medium

CVE-2026-44897 Mistune is a Python Markdown parser with renderers and plugins

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.

Affected products and versions

Product Affected versions Fixed in
mistune 3.2 earliest → < 3.2.1 3.2.1

References

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