CVE-2026-59927: Mistune Project Mistune

Medium severity, CVSS 5.3. EPSS: 0.5% chance of exploitation in the next 30 days.

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.

Affected products

• Mistune Project Mistune: before 3.3.0 (fixed in 3.3.0)

Published 2026-07-08. Last modified 2026-07-09.