VULNERABILITY INTELLIGENCE
CVE-2026-49851
CVSS score7.5 HIGH
EPSS probability0.52%
CISA KEVNot currently listed
Published2026-06-24
Last modified2026-10-25
CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Description
Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, Mistune is vulnerable to a CPU exhaustion DoS due to superlinear (approximately O(n²)) behavior in parse_link_text. When parsing Markdown containing many consecutive [ characters, parse_link_text repeatedly scans the input using a regex search inside a loop. Each iteration re-scans a large portion of the remaining string, resulting in quadratic-time behavior. An attacker-controlled Markdown input can therefore trigger excessive CPU usage with a very small payload. This vulnerability is fixed in 3.3.0.
Weakness classification
- security-advisories@github.com: CWE-400
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c: CWE-1333