CVE-2026-44708: Mistune math plugin XSS bypass in Markdown rendering

CVE-2026-44708 · Severity: medium · CVSS 6.1 · Published 2026-05-26

Mistune is a Python library used to convert Markdown text into HTML. A security flaw in its math plugin allows malicious users to bypass safety filters and inject harmful scripts into web pages. This could lead to unauthorized actions being performed in a user's browser, such as stealing session cookies or redirecting users to malicious sites.

Technologies: mistune (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2026-44708 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-44708 being exploited in the wild.
How severe is CVE-2026-44708?
Medium severity, with a CVSS score of 6.1, published 26 May 2026.
Which products and versions are affected?
mistune (PyPI) <= 3.2.0, ECOSYSTEM:introduced=0,fixed=3.2.1, ECOSYSTEM:introduced=0,last_affected=3.2.0.
Is there a fix for CVE-2026-44708?
Yes. mistune (PyPI): upgrade to 3.2.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-44708 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-44708?
Check whether you run mistune (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • mistune (PyPI): upgrade to 3.2.1 or later
    pip install "mistune>=3.2.1"

Technical details

A Cross-Site Scripting (XSS) vulnerability exists in the Mistune math plugin due to improper neutralization of input during HTML generation. The 'render_inline_math' and 'render_block_math' functions in 'src/mistune/plugins/math.py' concatenate raw user-supplied text directly into the HTML output without calling sanitization helpers or checking the renderer's '_escape' flag. This allows an attacker to bypass the 'escape=True' security configuration by wrapping malicious HTML/JavaScript inside math delimiters ($...$ or $$...$$). The vulnerability is fixed in version 3.2.1 by ensuring math content is properly escaped.

Affected products

  • lepture mistune < 3.2.1

Identifiers

  • CVE-2026-44708
  • GHSA-8g87-j6q8-g93x
  • PYSEC-2026-2206

Timeline

  • 2026-05-03: patched: Version 3.2.1 released with fixes for math escaping.
  • 2026-05-06: advisory: GitHub Security Advisory GHSA-8g87-j6q8-g93x published.
  • 2026-05-26: disclosed: CVE-2026-44708 published to the NVD.

References

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