Vulnerability in Lepture Mistune
CVE-2026-59927
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
EPSS exploit prediction
EPSS: 0.005 (43.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 43rd percentile — 43.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000
Affected products
- Lepture Mistune — versions < 3.3.0
- Mistune Project
Weakness classification (CWE)
References
- github.com/lepture/mistune/security/advisories/GHSA-8mpj-m6qm-5qr8 (Exploit, Third Party Advisory)
- github.com/lepture/mistune/commit/1bef343ade163fc3bb95572b15be720084cdb993 (Patch)
- github.com/lepture/mistune/releases/tag/v3.3.0 (Release Notes)
Frequently asked questions
- What is CVE-2026-59927?
- CVE-2026-59927 is a medium-severity vulnerability in Lepture Mistune, classified under Uncontrolled Recursion. CVSS score: 5.3/10. Published 2026-07-08.
- How severe is CVE-2026-59927?
- Medium severity. CVSS v3 base score is 5.3 out of 10.