CVE-2026-59928: CWE-407: Inefficient Algorithmic Complexity in lepture mistune
Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a Markdown document containing many repeated or distinct reference-link definitions causes quadratic work in src/mistune/block_parser.py and the ref_links environment dictionary handling, allowing denial of service through CPU exhaustion. This issue is fixed in version 3.3.0.
AI Analysis
Technical Summary
Mistune versions before 3.3.0 suffer from an inefficient algorithmic complexity issue (CWE-407) in the src/mistune/block_parser.py file and the ref_links environment dictionary handling. When processing Markdown documents with numerous repeated or distinct reference-link definitions, the parser performs quadratic work, which can be exploited to cause denial of service by exhausting CPU resources. The problem is resolved in version 3.3.0.
Potential Impact
An attacker can cause a denial of service condition by submitting specially crafted Markdown documents with many repeated or distinct reference-link definitions, leading to excessive CPU consumption and service disruption. There is no impact on confidentiality or integrity.
Mitigation Recommendations
Upgrade mistune to version 3.3.0 or later, where this inefficiency and associated denial of service vulnerability have been fixed. Patch status is confirmed by the version fix noted in the description. No additional vendor advisory is available to indicate alternative mitigations.
CVE-2026-59928: CWE-407: Inefficient Algorithmic Complexity in lepture mistune
Description
Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a Markdown document containing many repeated or distinct reference-link definitions causes quadratic work in src/mistune/block_parser.py and the ref_links environment dictionary handling, allowing denial of service through CPU exhaustion. This issue is fixed in version 3.3.0.
CVSS v3.1
Score 7.5high
Affected software
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Mistune versions before 3.3.0 suffer from an inefficient algorithmic complexity issue (CWE-407) in the src/mistune/block_parser.py file and the ref_links environment dictionary handling. When processing Markdown documents with numerous repeated or distinct reference-link definitions, the parser performs quadratic work, which can be exploited to cause denial of service by exhausting CPU resources. The problem is resolved in version 3.3.0.
Potential Impact
An attacker can cause a denial of service condition by submitting specially crafted Markdown documents with many repeated or distinct reference-link definitions, leading to excessive CPU consumption and service disruption. There is no impact on confidentiality or integrity.
Mitigation Recommendations
Upgrade mistune to version 3.3.0 or later, where this inefficiency and associated denial of service vulnerability have been fixed. Patch status is confirmed by the version fix noted in the description. No additional vendor advisory is available to indicate alternative mitigations.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-07-07T18:20:06.126Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a4e81d8c9d9e3dbe3746a5a
Added to database: 07/08/2026, 16:59:04 UTC
Last enriched: 07/08/2026, 17:13:22 UTC
Last updated: 08/22/2026, 22:52:15 UTC
Views: 83
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