CVE-2025-66400 MEDIUM

CVE-2025-66400: mdast-util-to-hast unsanitized class attribute

Vendor Syntax-Tree
Product mdast-util-to-hast
Weakness CWE-20 · Input validation
Published December 1, 2025
Last update December 2, 2025
View on NVD All CVEs

CVSS base score

6.9/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality —
Integrity —

CVSS 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

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

December 1, 2025 CVE published
December 2, 2025 Record updated