UBUNTU-CVE-2026-59925
Mistune, a Python Markdown parser, has a denial of service vulnerability in versions prior to 3.3.0. The issue arises from the parser performing quadratic work when processing long sequences of double-asterisk or triple-asterisk emphasis pairs, leading to excessive CPU usage. This flaw is fixed in version 3.3.0.
AI Analysis
Technical Summary
Mistune versions before 3.3.0 contain a denial of service vulnerability caused by inefficient parsing logic in src/mistune/inline_parser.py. Specifically, the parser scans forward for matching close markers from every potential opening run of double or triple asterisks, resulting in quadratic time complexity. This can be exploited by crafting input with long sequences of well-formed emphasis markers, causing high CPU consumption and denial of service. The vulnerability is resolved in Mistune version 3.3.0.
Potential Impact
An attacker can cause a denial of service by supplying specially crafted Markdown input that triggers excessive CPU usage during parsing. This does not affect confidentiality or integrity but impacts availability of services using vulnerable Mistune versions.
Mitigation Recommendations
Upgrade Mistune to version 3.3.0 or later, where this vulnerability is fixed. No other mitigations are indicated.
UBUNTU-CVE-2026-59925
Description
Mistune, a Python Markdown parser, has a denial of service vulnerability in versions prior to 3.3.0. The issue arises from the parser performing quadratic work when processing long sequences of double-asterisk or triple-asterisk emphasis pairs, leading to excessive CPU usage. This flaw is fixed in version 3.3.0.
CVSS v3.1
Score 7.5high
Affected software
pkg:deb/ubuntu/[email protected]?arch=source&distro=bionicpkg:deb/ubuntu/[email protected]+really0.8.4-1?arch=source&distro=jammypkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=resoluteRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Mistune versions before 3.3.0 contain a denial of service vulnerability caused by inefficient parsing logic in src/mistune/inline_parser.py. Specifically, the parser scans forward for matching close markers from every potential opening run of double or triple asterisks, resulting in quadratic time complexity. This can be exploited by crafting input with long sequences of well-formed emphasis markers, causing high CPU consumption and denial of service. The vulnerability is resolved in Mistune version 3.3.0.
Potential Impact
An attacker can cause a denial of service by supplying specially crafted Markdown input that triggers excessive CPU usage during parsing. This does not affect confidentiality or integrity but impacts availability of services using vulnerable Mistune versions.
Mitigation Recommendations
Upgrade Mistune to version 3.3.0 or later, where this vulnerability is fixed. No other mitigations are indicated.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-59925
- Osv Schema Version
- 1.7.0
- Aliases
- []
- Ecosystems
- ["Ubuntu:16.04:LTS","Ubuntu:18.04:LTS","Ubuntu:20.04:LTS","Ubuntu:22.04:LTS","Ubuntu:24.04:LTS","Ubuntu:25.10","Ubuntu:26.04:LTS"]
- Database Specific Severity
- null
- Cvss Version
- 3.1
Threat ID: 6a58b44f68715ace43d6b6fc
Added to database: 07/16/2026, 10:37:03 UTC
Last enriched: 07/16/2026, 11:30:39 UTC
Last updated: 07/31/2026, 19:24:50 UTC
Views: 4
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