Is CVE-2026-59926 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-59926 being exploited in the wild.

How severe is CVE-2026-59926?

Medium severity, with a CVSS score of 4, published 8 July 2026.

Which products and versions are affected?

mistune (PyPI) < 3.3.0, ECOSYSTEM:introduced=0,fixed=3.3.0.

Is there a fix for CVE-2026-59926?

Yes. mistune (PyPI): upgrade to 3.3.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-59926 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-59926?

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.

CVE-2026-59926: lepture Mistune XSS in Admonition directive

Q: Which products and versions are affected?

mistune (PyPI) < 3.3.0, ECOSYSTEM:introduced=0,fixed=3.3.0.

Q: Is there a fix for CVE-2026-59926?

Yes. mistune (PyPI): upgrade to 3.3.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

Q: How is CVE-2026-59926 attacked?

It is attacked over the network, in a software library.

Q: Am I affected by CVE-2026-59926?

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.

CVE-2026-59926 · Severity: medium · CVSS 4 · Published 2026-07-08

Mistune is a popular Python library used to convert Markdown text into HTML. A security flaw in its 'Admonition' feature allows attackers to inject malicious scripts into web pages. If a user views a page containing specially crafted Markdown, the attacker could potentially steal session information or perform unauthorized actions on the user's behalf.

Technologies: mistune (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2026-59926 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-59926 being exploited in the wild.
How severe is CVE-2026-59926?: Medium severity, with a CVSS score of 4, published 8 July 2026.
Which products and versions are affected?: mistune (PyPI) < 3.3.0, ECOSYSTEM:introduced=0,fixed=3.3.0.
Is there a fix for CVE-2026-59926?: Yes. mistune (PyPI): upgrade to 3.3.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-59926 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-59926?: 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 3.3.0 or later
```
pip install "mistune>=3.3.0"
```

Technical details

A Cross-Site Scripting (XSS) vulnerability exists in Mistune's Admonition directive implementation within `src/mistune/directives/admonition.py`. The `render_admonition()` function fails to escape the `:class:` option before concatenating it into the HTML class attribute. This oversight allows for attribute injection and XSS even when the `HTMLRenderer` is configured with `escape=True`. An attacker can exploit this by providing raw user input in the class option of an Admonition directive. The issue is resolved in version 3.3.0.

Affected products

lepture mistune < 3.3.0

Identifiers

CVE-2026-59926
GHSA-g97x-gvcm-x72h
PYSEC-2026-2214

Timeline

2026-06-21: disclosed
2026-07-08: advisory: NVD publication
2026-07-20: advisory: GitHub Advisory published

References

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