Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a run of closed tilde, equals-sign, or caret marker pairs around a character causes quadratic work in src/mistune/plugins/formatting.py when the strikethrough, mark, or insert plugin scans for matching markers from each possible start position, allowing denial of service through CPU exhaustion. This issue is fixed in version 3.3.0.
Fix
Patch, vendor advisory and mitigation references on NVD 3
- https://github.com/lepture/mistune/commit/96d0f57f8fe9eeb06bb4cff521962a27d7c402e7 Patch
- https://github.com/lepture/mistune/security/advisories/GHSA-c8j7-8cv4-2xmq Exploit, Vendor Advisory
- https://github.com/lepture/mistune/security/advisories/GHSA-c8j7-8cv4-2xmq Exploit, Vendor Advisory
Every line above is quoted from NVD, CISA, Microsoft, the vendor's own advisory or DISA; nothing is generated.
Change history 1
- First seenCVSS 7.5 · mistune_projectNVD modified 2026-10-25 17:10
Affected (CPE criteria) 1
cpe:2.3:a:mistune_project:mistune:*:*:*:*:*:*:*:*
References 4
- https://github.com/lepture/mistune/commit/96d0f57f8fe9eeb06bb4cff521962a27d7c402e7 Patch
- https://github.com/lepture/mistune/releases/tag/v3.3.0 Release Notes
- https://github.com/lepture/mistune/security/advisories/GHSA-c8j7-8cv4-2xmq Exploit, Vendor Advisory
- https://github.com/lepture/mistune/security/advisories/GHSA-c8j7-8cv4-2xmq Exploit, Vendor Advisory