---
id: CVE-2026-111766
title: >-
  markdown-it: Quadratic-time denial of service in inline HTML parsing with html
  enabled
summary: >-
  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 com…
severity: low
cvss: 3.7
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L'
cvssSource: cna
cwe:
  - CWE-400
  - CWE-407
vendor: markdown-it
product: markdown-it
affected:
  - 'markdown-it >= 15.0.0, < 15.0.3'
  - markdown-it < 14.3.3
published: '2026-10-19'
updated: '2026-10-19'
sourceUpdated: '2026-10-19T19:47:46.488Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-111766'
references:
  - url: >-
      https://github.com/markdown-it/markdown-it/security/advisories/GHSA-vfgh-jcmw-g37q
    label: >-
      https://github.com/markdown-it/markdown-it/security/advisories/GHSA-vfgh-jcmw-g37q
  - url: >-
      https://github.com/markdown-it/markdown-it/commit/928bc8c11ded60181c0e7fc5aa954eec582e8e79
    label: >-
      https://github.com/markdown-it/markdown-it/commit/928bc8c11ded60181c0e7fc5aa954eec582e8e79
  - url: >-
      https://github.com/markdown-it/markdown-it/commit/d99f48839d37af6fd8a2617516c43dab90755503
    label: >-
      https://github.com/markdown-it/markdown-it/commit/d99f48839d37af6fd8a2617516c43dab90755503
  - url: 'https://github.com/markdown-it/markdown-it/releases/tag/14.3.3'
    label: 'https://github.com/markdown-it/markdown-it/releases/tag/14.3.3'
  - url: 'https://github.com/markdown-it/markdown-it/releases/tag/15.0.3'
    label: 'https://github.com/markdown-it/markdown-it/releases/tag/15.0.3'
tags:
  - cve.org
ingestedAt: '2026-10-19T20:41:18.453Z'
---

## Overview

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

- `markdown-it >= 15.0.0, < 15.0.3`
- `markdown-it < 14.3.3`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.