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Description

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.

PUBLISHED Reserved 2026-07-07 | Published 2026-07-08 | Updated 2026-07-09 | Assigner GitHub_M




HIGH: 7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Problem types

CWE-407: Inefficient Algorithmic Complexity

CWE-1333: Inefficient Regular Expression Complexity

Product status

< 3.3.0
affected

References

github.com/...istune/security/advisories/GHSA-c8j7-8cv4-2xmq exploit

github.com/...istune/security/advisories/GHSA-c8j7-8cv4-2xmq

github.com/...ommit/96d0f57f8fe9eeb06bb4cff521962a27d7c402e7

github.com/lepture/mistune/releases/tag/v3.3.0

cve.org (CVE-2026-59922)

nvd.nist.gov (CVE-2026-59922)

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