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OpenAdvisories
Low · 3.7 CVE-2026-111766 EUVD-2026-104595GHSA-vfgh-jcmw-g37q

markdown-it: Quadratic-time denial of service in inline HTML parsing with html enabled

Published Oct 19, 2026 · Updated Oct 26, 2026 · Assigned by GitHub_M

Description

markdown-it is a Markdown parser. Prior to 14.3.3 and 15.0.3, when the html option or commonmark preset is enabled and the constructs occur inside a paragraph, attacker-controlled Markdown containing repeated unterminated inline HTML comments, processing instructions, declarations, or CDATA sections reaches src/rules_inline/html_inline.ts. Its HTML_TAG_RE match searches the remaining suffix for the appropriate terminator; when no terminator is present, parsing advances to the next opener and repeats the match over overlapping input, causing quadratic processing and denial of service through event-loop blocking or an unresponsive browser main thread. HTML blocks and the default HTML-disabled configuration are not affected by these payloads. This issue is fixed in versions 14.3.3 and 15.0.3.

Affected products

VendorProductAffectedFixed
markdown-it markdown-it >= 15.0.0, < 15.0.3, < 14.3.3 —

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

ReleasePackageFixed inAdvisory
Debian 14 node-markdown-it No fix yet —
Debian 13 node-markdown-it No fix yet —
Debian 12 node-markdown-it No fix yet —
ReleasePackageFixed inAdvisory
Ubuntu 26.10 node-markdown-it No fix yet —
Ubuntu 26.04 LTS node-markdown-it No fix yet —
Ubuntu 24.04 LTS node-markdown-it No fix yet —
Ubuntu 22.04 LTS node-markdown-it No fix yet —

Wolfi

ReleasePackageFixed inAdvisory
Wolfi rolling renovate 44.176.1-r0 —

Affected packages

EcosystemPackageAffectedFixedRecord
npm markdown-it < 14.3.3 14.3.3 GHSA-vfgh-jcmw-g37q
npm markdown-it >= 15.0.0, < 15.0.3 15.0.3 GHSA-vfgh-jcmw-g37q

References