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

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Summary

CVECVE-2026-59925
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-08 17:17:28 UTC
Updated2026-07-09 19:39:58 UTC
DescriptionMistune 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.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from [email protected]

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

EPSS: 0.003580000 probability, percentile 0.279110000 (date 2026-07-10)

Problem Types: CWE-407 | CWE-1333 | CWE-407 CWE-407: Inefficient Algorithmic Complexity | CWE-1333 CWE-1333: Inefficient Regular Expression Complexity

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Mistune Project Mistune All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Lepture Mistune affected < 3.3.0 Not specified

References

ReferenceSourceLinkTags
github.com/lepture/mistune/commit/5de41fb8e527004dbc363e047a3c380c9288c74f [email protected] github.com Patch
github.com/lepture/mistune/security/advisories/GHSA-4j32-57v6-6g45 [email protected] github.com Exploit, Vendor Advisory
github.com/lepture/mistune/releases/tag/v3.3.0 [email protected] github.com Release Notes
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis
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