CVE-2026-115350: Mistune before 3.3.0 Stored XSS via Include Directive HTML Files

Q: Which deployments are exposed to this issue?

Deployments using Mistune before 3.3.0 are exposed when the Include directive is enabled or available, rendering is performed with escape=False, and an attacker can cause a readable HTML-family file to be included.

Q: What does an attacker need to exploit it?

The attacker needs to plant an .html, .xhtml, or .htm file that the renderer can read, then reference it through an include directive. The issue can be combined with path traversal to reach the planted file.

Q: Is a default escaped rendering configuration affected?

The provided information identifies exploitation when escape=False is set. It does not establish that rendering with escaping enabled is affected.

Published Oct 22, 2026

Updated

Mistune before 3.3.0 contains a cross-site scripting vulnerability in the Include directive that emits included .html, .xhtml, or .htm file content as raw blockhtml tokens. Attackers who can plant an HTML file readable by the renderer can reference it via an include directive, combined with path traversal, to execute stored scripts when escape=False is set.

Affected Software

1 affected component

pypi/mistune<3.3.0

Event History

Oct 22, 2026

CVE Published

via MITRE·07:13 PM

Data Sourced

via MITRE·07:13 PM

DescriptionSeverityWeakness

Frequently Asked Questions

Which deployments are exposed to this issue?

Deployments using Mistune before 3.3.0 are exposed when the Include directive is enabled or available, rendering is performed with escape=False, and an attacker can cause a readable HTML-family file to be included.

What does an attacker need to exploit it?

The attacker needs to plant an .html, .xhtml, or .htm file that the renderer can read, then reference it through an include directive. The issue can be combined with path traversal to reach the planted file.

Is a default escaped rendering configuration affected?

The provided information identifies exploitation when escape=False is set. It does not establish that rendering with escaping enabled is affected.

CVE-2026-115350: Mistune before 3.3.0 Stored XSS via Include Directive HTML Files

Affected Software

Event History

Frequently Asked Questions

Which deployments are exposed to this issue?

What does an attacker need to exploit it?

Is a default escaped rendering configuration affected?

Company

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Frequently Asked Questions

Which deployments are exposed to this issue?

What does an attacker need to exploit it?

Is a default escaped rendering configuration affected?