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.

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.0041.

Exploitation none

Automatable yes

Technical Impact partial

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
lepture mistune affected
Version Status Constraints
< 3.3.0 affected —

No data.

No data.

OpenCVE Enrichment is a feature of OpenCVE that uses AI to automatically link vendors and products to CVEs. Learn more on GitHub.

Vendors Products
Lepture Subscribe
Mistune Subscribe

Project Subscriptions

Vendors Products
Lepture Subscribe
Mistune Subscribe
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
Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/lepture/mistune/commit/5de41fb8e527004dbc363e047a3c380c9288c74f cve-icon cve-icon
https://github.com/lepture/mistune/releases/tag/v3.3.0 cve-icon cve-icon
https://github.com/lepture/mistune/security/advisories/GHSA-4j32-57v6-6g45 cve-icon cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2026-59925 cve-icon
https://www.cve.org/CVERecord?id=CVE-2026-59925 cve-icon
History

Fri, 10 Jul 2026 00:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

 threat_severity

Moderate

Wed, 08 Jul 2026 20:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

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

Wed, 08 Jul 2026 17:45:00 +0000

Type Values Removed Values Added
First Time appeared Lepture
Lepture mistune
Vendors & Products Lepture
Lepture mistune

Wed, 08 Jul 2026 16:30:00 +0000

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'}

Projects

Sign in to view the affected projects.

cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-07-08T19:44:48.084Z

Reserved: 2026-07-07T18:20:06.126Z

Link: CVE-2026-59925

cve-icon Vulnrichment

Updated: 2026-07-08T19:44:45.485Z

cve-icon NVD

No data.

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-07-08T16:18:43Z

Links: CVE-2026-59925 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-07-23T11:30:17Z

Weaknesses