CVE-2026-59925: CWE-407: Inefficient Algorithmic Complexity in lepture mistune
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.
AI Analysis
Technical Summary
CVE-2026-59925 describes an inefficient algorithmic complexity vulnerability (CWE-407) in the Mistune Python Markdown parser before version 3.3.0. The vulnerability occurs in src/mistune/inline_parser.py, where the parser performs quadratic work when processing long sequences of double- or triple-asterisk emphasis pairs. This inefficiency can be exploited to cause denial of service by consuming excessive CPU resources during parsing. The issue is resolved in Mistune version 3.3.0.
Potential Impact
An attacker can cause a denial of service by triggering the parser to perform excessive CPU work when parsing specially crafted Markdown input containing long sequences of double- or triple-asterisk emphasis pairs. This leads to service unavailability or degraded performance. There is no impact on confidentiality or integrity.
Mitigation Recommendations
Upgrade to Mistune version 3.3.0 or later, where this inefficient parsing issue is fixed. No other mitigation is indicated or required.
CVE-2026-59925: CWE-407: Inefficient Algorithmic Complexity in lepture mistune
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.
CVSS v3.1
Score 7.5high
Affected software
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-59925 describes an inefficient algorithmic complexity vulnerability (CWE-407) in the Mistune Python Markdown parser before version 3.3.0. The vulnerability occurs in src/mistune/inline_parser.py, where the parser performs quadratic work when processing long sequences of double- or triple-asterisk emphasis pairs. This inefficiency can be exploited to cause denial of service by consuming excessive CPU resources during parsing. The issue is resolved in Mistune version 3.3.0.
Potential Impact
An attacker can cause a denial of service by triggering the parser to perform excessive CPU work when parsing specially crafted Markdown input containing long sequences of double- or triple-asterisk emphasis pairs. This leads to service unavailability or degraded performance. There is no impact on confidentiality or integrity.
Mitigation Recommendations
Upgrade to Mistune version 3.3.0 or later, where this inefficient parsing issue is fixed. No other mitigation is indicated or required.
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: 6a4e7ad5c9d9e3dbe36a7df3
Added to database: 07/08/2026, 16:29:09 UTC
Last enriched: 07/08/2026, 16:43:16 UTC
Last updated: 08/22/2026, 10:52:10 UTC
Views: 93
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