CVE-2026-44897 Details
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.
A cross-site scripting vulnerability has been identified in the Mistune Markdown parser, prior to version 3.2.1. The issue arises in the HTMLRenderer.heading() method, which constructs heading tags by directly concatenating the id attribute value into the HTML without proper sanitization. This flaw allows an attacker to inject arbitrary attributes, such as event handlers or links, into the heading element. The vulnerability is exploitable when the id value includes a double-quote character, which disrupts the attribute formatting and enables the injection.
Users should update to Mistune version 3.2.1 or later, where this vulnerability has been fixed.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jun 1, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/lepture/mistune/releases/tag/v3.2.1 | [email protected] | ProductRelease Notes |
| https://github.com/lepture/mistune/security/advisories/GHSA-v87v-83h2-53w7 | [email protected] | ExploitVendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-79 | Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| mistune project mistune | < 3.2.1 |
CPE
Remediation
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Change History
6 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 24, 2026 | CVE Translated | [email protected] |
| Jul 23, 2026 | CVE Translated | [email protected] |
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| May 28, 2026 | Initial Analysis | [email protected] |
| May 26, 2026 | New CVE Received | [email protected] |