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Description

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, long sequences of well-formed double-asterisk or triple-asterisk emphasis pairs around a character cause quadratic work in src/mistune/inline_parser.py because the parser scans forward for matching close markers from every potential opening run, allowing denial of service in default Mistune parsing. This issue is fixed in version 3.3.0.

PUBLISHED Reserved 2026-07-07 | Published 2026-07-08 | Updated 2026-07-08 | 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-4j32-57v6-6g45

github.com/...ommit/5de41fb8e527004dbc363e047a3c380c9288c74f

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

cve.org (CVE-2026-59925)

nvd.nist.gov (CVE-2026-59925)

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