CVE-2026-121438 — Vulnerability intelligence
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Published:
- CVSS
- 6.9
- CISA KEV
- Not listed; not proof of no exploitation
Original source text (not a translation)
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.