CVE-2026-59927

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

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

lepture · mistune

CVSS v3.1 GITHUB

5.3 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS

0.53% chance of exploitation in the next 30 days, 44th percentile

Published

2026-07-08

Proof-of-concept exploits (1)

• advisories/GHSA-8mpj-m6qm-5qr8

Security advisories

• lepture/mistune/security/advisories/GHSA-8mpj-m6qm-5qr8
• lepture/mistune/commit/1bef343ade163fc3bb95572b15be720084cdb993

References

• CVE Record
• NVD entry