CVE-2026-59925

inline_parser: quadratic-time parsing on long runs of `**x**` and `***x***` emphasis pairs

Published Jul 8, 2026 CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-4j32-57v6-6g45 Mistune inline_parser: quadratic-time parsing on long runs of `**x**` and `***x***` emphasis pairs
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Lepture
Lepture mistune
Vendors & Products Lepture
Lepture mistune
Type Values Removed Values Added
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.
Title inline_parser: quadratic-time parsing on long runs of `**x**` and `***x***` emphasis pairs
Weaknesses CWE-1333
CWE-407
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Jul 8, 2026, 7:44 PM
Reserved
Jul 7, 2026, 6:20 PM
Status
Analyzed
Published
Jul 8, 2026, 5:17 PM
Modified
Oct 25, 2026, 5:10 PM
Severity
Moderate
Public date
Jul 8, 2026, 4:18 PM