Lepture
CVE-2026-121437: Mistune from 3.3.0 before 3.3.4 contains a denial of service vulnerability that allows remote attackers to exhaust CPU through quadratic-time emphasis delimiter
CVE-2026-121437 Nov 3, 2026 Source: Vendor
Mistune from 3.3.0 before 3.3.4 contains a denial of service vulnerability that allows remote attackers to exhaust CPU through quadratic-time emphasis delimiter processing. Attackers can submit small markdown documents with repeated patterns like "*a_b" to trigger an O(n²) index-fixup loop, stalling workers for seconds.
Source of record
The credited names below are quoted verbatim from the vendor's own advisory:
https://nvd.nist.gov/vuln/detail/CVE-2026-121437
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