CVE-2026-59927Mistune directives/include: mutual `.. include::` recursion crashes the renderer with `RecursionError`, denial of service via two attacker-controlled markdown files

Description

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, the Include directive in src/mistune/directives/include.py detects only direct self-includes and not indirect cycles, allowing two markdown files that include each other to trigger unbounded recursion, raise RecursionError, and crash the rendering request. This issue is fixed in version 3.3.0.

Data: CVE.org, NVD, CISA KEV, FIRST EPSS, Ubuntu. Published as the sources state it, in English.

Affected products and versions

References and patches

• https://github.com/lepture/mistune/security/advisories/GHSA-8mpj-m6qm-5qr8 ExploitThird Party Advisory
• https://github.com/lepture/mistune/commit/1bef343ade163fc3bb95572b15be720084cdb993 Patch
• https://github.com/lepture/mistune/releases/tag/v3.3.0 Release Notes