CVE-2026-59922

Summary

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a run of closed tilde, equals-sign, or caret marker pairs around a character causes quadratic work in src/mistune/plugins/formatting.py when the strikethrough, mark, or insert plugin scans for matching markers from each possible start position, allowing denial of service through CPU exhaustion. This issue is fixed in version 3.3.0.

Affected Software

Weaknesses

• CWE-407: CWE-407: Inefficient Algorithmic Complexity
• CWE-1333: CWE-1333: Inefficient Regular Expression Complexity

References

• https://github.com/lepture/mistune/security/advisories/GHSA-c8j7-8cv4-2xmq
• https://github.com/lepture/mistune/commit/96d0f57f8fe9eeb06bb4cff521962a27d7c402e7
• https://github.com/lepture/mistune/releases/tag/v3.3.0

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