Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, render_toc_ul() builds a <ul> table-of-contents tree from a list of (level, id, text) tuples. Both the id value (used as href="#<id>") and the text value (used as the visible link label) are inserted into <a> tags via a plain Python format string — with no HTML escaping applied to either value. When heading IDs are derived from user-supplied heading text (the standard use-case for readable slug anchors), an attacker can craft a heading whose text breaks out of the href="#..." attribute context, injecting arbitrary HTML tags including <script> blocks directly into the rendered TOC. This vulnerability is fixed in 3.2.1.
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History
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, render_toc_ul() builds a <ul> table-of-contents tree from a list of (level, id, text) tuples. Both the id value (used as href="#<id>") and the text value (used as the visible link label) are inserted into <a> tags via a plain Python format string — with no HTML escaping applied to either value. When heading IDs are derived from user-supplied heading text (the standard use-case for readable slug anchors), an attacker can craft a heading whose text breaks out of the href="#..." attribute context, injecting arbitrary HTML tags including <script> blocks directly into the rendered TOC. This vulnerability is fixed in 3.2.1. | |
| Title | Mistune TOC Anchor Injection XSS | |
| Weaknesses | CWE-79 | |
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cvssV3_1
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-05-26T20:41:53.805Z
Reserved: 2026-05-07T21:50:33.546Z
Link: CVE-2026-44898
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Status : Received
Published: 2026-05-26T21:16:39.810
Modified: 2026-05-26T21:16:39.810
Link: CVE-2026-44898
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OpenCVE Enrichment
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