high7.5
CVE-2026-59925
Mistune inline_parser: quadratic-time parsing on long runs of `**x**` and `***x***` emphasis pairs
Impact
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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| pip | mistune | < 3.3.0 | 3.3.0 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Mistune Project | Mistune | before 3.3.0 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-4j32-57v6-6g45
- https://github.com/lepture/mistune/security/advisories/GHSA-4j32-57v6-6g45
- https://nvd.nist.gov/vuln/detail/CVE-2026-59925
- https://github.com/lepture/mistune/commit/5de41fb8e527004dbc363e047a3c380c9288c74f
- https://github.com/lepture/mistune/releases/tag/v3.3.0
- https://github.com/pypa/advisory-database/tree/main/vulns/mistune/PYSEC-2026-2213.yaml