lepture Mistune up to 3.2.0 Admonition Directive admonition.py render_admonition Class cross site scripting

Summaryinfo

A vulnerability has been found in lepture Mistune up to 3.2.0 and classified as problematic. This affects the function render_admonition of the file src/mistune/directives/admonition.py of the component Admonition Directive. This manipulation of the argument Class causes cross site scripting. The identification of this vulnerability is CVE-2026-59926. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability classified as problematic was found in lepture Mistune up to 3.2.0. Affected by this vulnerability is the function render_admonition of the file src/mistune/directives/admonition.py of the component Admonition Directive. The manipulation of the argument class with an unknown input leads to a cross site scripting vulnerability. The CWE definition for the vulnerability is CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. As an impact it is known to affect integrity. The summary by CVE is:

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, render_admonition() in src/mistune/directives/admonition.py concatenates the Admonition directive :class: option into the HTML class attribute without escaping, allowing attribute injection and cross-site scripting even when HTMLRenderer escape mode is enabled. This issue is fixed in version 3.2.1.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-59926 since 07/07/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1059.007 according to MITRE ATT&CK.

Upgrading to version 3.2.1 eliminates this vulnerability.

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Vendor

• lepture

Name

• Mistune

Version

• 3.0
• 3.1
• 3.2.0

Website

• Product: https://github.com/lepture/mistune/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Discussion