CVE-2026-121438
MEDIUM
NVD
CVSS Score
5.3
Severity
MEDIUM
Published
Nov 03, 2026
Vendor
unknown
Description
Mistune before 3.3.3 contains a denial of service vulnerability in InlineParser.parse_link that allows attackers to cause quadratic CPU growth by supplying balanced nested brackets. Attackers can submit crafted Markdown with thousands of nested bracket pairs not forming a valid link, triggering repeated _contains_nested_link scans that exhaust CPU in parsing applications.