Vulnerability 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.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Mistune Project | Mistune | < 3.2.1 |
Related Weaknesses (CWE)
References
- https://github.com/lepture/mistune/releases/tag/v3.2.1ProductRelease Notes
- https://github.com/lepture/mistune/security/advisories/GHSA-6269-cqxg-mhhvExploitVendor Advisory
- https://github.com/lepture/mistune/security/advisories/GHSA-6269-cqxg-mhhvExploitVendor Advisory
FAQ
What is CVE-2026-44898?
CVE-2026-44898 is a vulnerability with a CVSS score of 6.1 (MEDIUM). 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...
How severe is CVE-2026-44898?
CVE-2026-44898 has been rated MEDIUM with a CVSS base score of 6.1/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-44898?
Check the references section above for vendor advisories and patch information. Affected products include: Mistune Project Mistune.