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[ CVE-2026-111758 · Published 20 Oct 2026 ]

markdown-it: Quadratic-time rendering of a single multi-line link reference definition with default options (regression since 14.0)

CVSS 7.5 EPSS <1%Fix available

[ Description ]Official description

markdown-it is a Markdown parser. From versions 14.1.0 to before 14.3.3, and 15.0.0 to before 15.0.3, a link reference definition whose label or title is never closed is O(n²) with default options. Continuation lines are pulled lazily with str += lineContent in src/rules_block/reference.ts, and the subsequent charCodeAt and slice calls flatten the V8 cons-string, copying everything collected so far; this runs before the rule decides the definition is invalid. No options are required to trigger it. This issue has been patched in versions 14.3.3 and 15.0.3.

[ Fixes ]Fixes and patches

  • markdown-it 14.3.3Fixed version · GitHub Advisories · npm package markdown-it: upgrade to 14.3.3 or later (affected >= 14.1.0, < 14.3.3)
  • markdown-it 15.0.3Fixed version · GitHub Advisories · npm package markdown-it: upgrade to 15.0.3 or later (affected >= 15.0.0, < 15.0.3)

[ Packages ]Affected open-source packages

[ References ]References