markdown-it up to 14.3.2/15.0.2 Inline HTML Parser html_inline.ts resource consumption

Summaryinfo

A vulnerability marked as problematic has been reported in markdown-it up to 14.3.2/15.0.2. Affected is an unknown function of the file src/rules_inline/html_inline.ts of the component Inline HTML Parser. The manipulation leads to resource consumption. This vulnerability is documented as CVE-2026-111766. The attack can be initiated remotely. There is not any exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in markdown-it up to 14.3.2/15.0.2. It has been rated as problematic. This issue affects an unknown code of the file src/rules_inline/html_inline.ts of the component Inline HTML Parser. The manipulation with an unknown input leads to a resource consumption vulnerability. Using CWE to declare the problem leads to CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. Impacted is availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-111766 since 10/16/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

Upgrading to version 14.3.3 or 15.0.3 eliminates this vulnerability.

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Productinfo

Name

• markdown-it

Version

• 14.3.0
• 14.3.1
• 14.3.2
• 15.0.0
• 15.0.1
• 15.0.2

Website

• Product: https://github.com/markdown-it/markdown-it/

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