CVE-2025-66400

mdast-util-to-hast unsanitized class attribute

Published Dec 1, 2025 CVSS 4.0 · 6.9 Medium EPSS < 1% KEV · Not listed
Description
mdast-util-to-hast is an mdast utility to transform to hast. From 13.0.0 to before 13.2.1, multiple (unprefixed) classnames could be added in markdown source by using character references. This could make rendered user supplied markdown code elements appear like the rest of the page. This vulnerability is fixed in 13.2.1.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-4fh9-h7wg-q85m mdast-util-to-hast has unsanitized class attribute
History
Type Values Removed Values Added
First Time appeared Unifiedjs
Unifiedjs mdast-util-to-hast
CPEs cpe:2.3:a:syntax-tree:mdast-util-to-hast:*:*:*:*:*:*:*:* cpe:2.3:a:unifiedjs:mdast-util-to-hast:*:*:*:*:*:node.js:*:*
Vendors & Products Unifiedjs
Unifiedjs mdast-util-to-hast
Type Values Removed Values Added
Weaknesses NVD-CWE-Other
CPEs cpe:2.3:a:syntax-tree:mdast-util-to-hast:*:*:*:*:*:*:*:*
Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N'}

threat_severity

Moderate

Type Values Removed Values Added
First Time appeared Syntax-tree
Syntax-tree mdast-util-to-hast
Vendors & Products Syntax-tree
Syntax-tree mdast-util-to-hast
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description mdast-util-to-hast is an mdast utility to transform to hast. From 13.0.0 to before 13.2.1, multiple (unprefixed) classnames could be added in markdown source by using character references. This could make rendered user supplied markdown code elements appear like the rest of the page. This vulnerability is fixed in 13.2.1.
Title mdast-util-to-hast unsanitized class attribute
Weaknesses CWE-20
CWE-915
References
Metrics cvssV4_0

{'score': 6.9, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N'}

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Dec 2, 2025, 3:34 PM
Reserved
Nov 28, 2025, 11:33 PM
Status
Analyzed
Published
Dec 1, 2025, 11:15 PM
Modified
Oct 18, 2026, 6:10 PM
Severity
Moderate
Public date
Dec 1, 2025, 10:17 PM