CVE-2026-44898: Mistune TOC Anchor Injection XSS

Analyzed

AliasesSUSE-SU-2026:2949-1GHSA-6269-cqxg-mhhvPYSEC-2026-2208+2 more

Published 26-05-2026Last modified 27-05-2026

Vulnerability summary

CVE-2026-44898 is a medium (CVSS 6.1) vulnerability in lepture mistune. EPSS estimates a 0.23% chance of exploitation in the next 30 days, higher than 13.6% of scored vulnerabilities. 1 public exploit is recorded.

Priority

Routine

Not severe (CVSS 6.1, network access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?

CVSS score

6.1/10

010

Medium · v3.1 (CVE.org)

EPSS score

0.23%

0%100%

Low · -0.04 pp in 30 days

KEVNot listedNot listed by any tracked catalog.

RansomwareNot flaggedNo ransomware use recorded.

Public exploits1github

Advisory lineage

Upstream 0 · Downstream 1

MGASA-2026-0254

Timeline

26-05-2026
PublishedVulnerability first disclosed.
27-05-2026
Last modifiedVulnerability information updated.

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.