What’s Vulnerable › Vulnerabilities

CVE-2026-76098: Mistune has Denial of Service — RecursionError via Excessive Emphasis Markers in Markdown

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-24 · updated 2026-10-12
• Weakness: CWE-674

Description

Mistune is a Python Markdown parser with renderers and plugins. Versions 3.3.0 through 3.3.2 are vulnerable to DoS through deeply nested tokens. HTML rendering creates deeply nested emphasis tokens from consecutive asterisk characters, and recursive rendering in HTMLRenderer.render_token() can exceed Python's recursion limit and raise RecursionError, allowing crafted Markdown to crash a parsing process. This issue is fixed in version 3.3.3

Affected products

• lepture mistune: from 3.3.0, < 3.3.3

References

• https://github.com/lepture/mistune/commit/0938fb7
• https://github.com/lepture/mistune/security/advisories/GHSA-6m44-fpc8-c3rq
• https://github.com/lepture/mistune/security/advisories/GHSA-6m44-fpc8-c3rq

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