Mistune Heading ID Attribute Injection XSS (lepture mistune)
At a glance
- Source
- NVD
- EPSS
- EPSS 0.23 % · percentile 14 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- GitHub_M
- NVD status
- Analyzed
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.
Weaknesses (CWE)
- CWE-79 — Improper Neutralization of Input During Web Page Generation
References
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | MEDIUM 6.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N | GitHub_M |
| CVSS 3.1 | MEDIUM 6.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N | NVD · security-advisories@github.com (Secondary) |
Advisories
- GHSA-v87v-83h2-53w7 — Mistune Heading ID Attribute has Injection XSS
- PYSEC-2026-2207 — 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 i
European references
- ENISA EUVD · EUVD-2026-31994
- GCVE · GCVE-0-2026-44897
Affected configurations (NVD CPE)
cpe:2.3:a:mistune_project:mistune:*:*:*:*:*:*:*:*< 3.2.1
Affected products
| Product | Versions |
|---|---|
| lepture · mistune | affected < 3.2.1 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |