PT-2026-41146 · Debian+4 · Mistune+1

Across-Verticals-Malaysia + 1 · Published 2026-05-14 · Updated 2026-05-26 · CVE-2026-44898

Positive Technologies (AI Summary)

CVSS v3.1

6.1

Medium

Base vector

AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Name of the Vulnerable Software and Affected Versions Mistune versions prior to 3.2.1

Description The render toc ul() function builds a table-of-contents tree from a list of tuples. The id value, used for the href attribute, and the text value, used as the link label, are inserted into <a> tags using a plain Python format string without HTML escaping. When heading IDs are derived from user-supplied text, an attacker can craft a heading that breaks out of the href attribute context to inject arbitrary HTML tags, such as <script> blocks, directly into the rendered table of contents. This occurs specifically within the render toc ul() function located in src/mistune/toc.py.

Recommendations Update to version 3.2.1. As a temporary workaround, restrict the use of custom heading id callbacks that return raw user-supplied text as the ID.

Exploit

Fix

XSS

Weakness Enumeration

CWE-79

Related Identifiers

CVE-2026-44898

GHSA-6269-CQXG-MHHV

Affected Products

Mistune

Mistune0

References · 11

• 🔥 https://github.com/lepture/mistune/security/advisories/GHSA-6269-cqxg-mhhv · Exploit
• https://osv.dev/vulnerability/DEBIAN-CVE-2026-44898 · Vendor Advisory
• https://osv.dev/vulnerability/UBUNTU-CVE-2026-44898 · Vendor Advisory
• https://security-tracker.debian.org/tracker/CVE-2026-44898 · Vendor Advisory
• https://ubuntu.com/security/CVE-2026-44898 · Vendor Advisory
• https://osv.dev/vulnerability/GHSA-6269-cqxg-mhhv · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-44898 · Security Note
• https://cve.org/CVERecord?id=CVE-2026-44898 · Security Note
• https://github.com/lepture/mistune/releases/tag/v3.2.1 · Note
• https://github.com/lepture/mistune/commit/04880a0 · Note
• https://github.com/lepture/mistune · Note