CVE-2026-59922
High
Description
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.
SeverityHigh
CVSS7.5
Exploit probability—
ProductMistune
PublishedJul 8, 2026
First seenJul 8, 2026
Weakness typeCWE-407CWE-407CWE-1333CWE-1333
How to fix
Update
- mistune_project mistune3.3.0 or later
- mistune3.3.0 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mistune_project mistune | v < 3.3.0 | 3.3.0 |
| mistunePyPI | v < 3.3.0 | 3.3.0 |
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