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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-111766
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-19 20:17:52 UTC
Updated2026-10-19 20:17:52 UTC
Descriptionmarkdown-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.

Risk And Classification

Primary CVSS: v3.1 3.7 LOW from [email protected]

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

Problem Types: CWE-400 | CWE-407 | CWE-400 CWE-400: Uncontrolled Resource Consumption | CWE-407 CWE-407: Inefficient Algorithmic Complexity

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary3.7LOWCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
3.1CNADECLARED3.7LOWCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Markdown-it Markdown-it affected >= 15.0.0, < 15.0.3 Not specified
CNA Markdown-it Markdown-it affected < 14.3.3 Not specified

References

ReferenceSourceLinkTags
github.com/markdown-it/markdown-it/releases/tag/15.0.3 [email protected] github.com
github.com/markdown-it/markdown-it/releases/tag/14.3.3 [email protected] github.com
github.com/markdown-it/markdown-it/commit/d99f48839d37af6fd8a2617516c43d... [email protected] github.com
github.com/markdown-it/markdown-it/security/advisories/GHSA-vfgh-jcmw-g37q [email protected] github.com
github.com/markdown-it/markdown-it/commit/928bc8c11ded60181c0e7fc5aa954e... [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

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