CVE-2026-121438

5.3 MEDIUMpublic exploit available

Published 2026-11-03 · Updated 2026-11-03

AI analysis for this CVE has not been generated yet. Raw NVD data is shown below.

NVD 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.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Weaknesses

CWE-400

Public exploit & PoC references

https://github.com/lepture/mistune/commit/fe02f40faf091f86da9ed62c865f31e11da111d7
https://github.com/lepture/mistune/security/advisories/GHSA-47p6-w2rc-5qf7

All references

https://github.com/lepture/mistune/commit/fe02f40faf091f86da9ed62c865f31e11da111d7
https://github.com/lepture/mistune/security/advisories/GHSA-47p6-w2rc-5qf7
https://www.vulncheck.com/advisories/mistune-before-3.3.3-denial-of-service-via-balanced-bracket-link-parsing

Source data: NVD (nvd.nist.gov), public domain. Exploit-DB.ai adds local AI analysis for defensive use only.

Related CVEs

HIGHCVE-2025-52290
HIGHCVE-2026-100137
HIGHCVE-2026-100138
HIGHCVE-2026-100139
HIGHCVE-2026-100242PoC
MEDIUMCVE-2026-100350PoC
MEDIUMCVE-2026-100527PoC
LOWCVE-2026-100542PoC

Related by shared AI tags and CWE weakness class. Browse the full archive.