CVE-2025-66400 - CVE House
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Status published Medium CVE-2025-66400

mdast-util-to-hast unsanitized class attribute

Vulnerability 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.

Impact Analysis

Refer to official advisory for detailed impact metrics.

Remediation

Ensure systems are updated to the latest vendor-supplied patch levels.

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Credits & Attribution

No credits recorded in the NVD database.

References

Affected Vendor

syntax-tree

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Affected Software

mdast-util-to-hast
Vulnerable Versions:
>= 13.0.0, < 13.2.1

Timeline

Official Publish: December 1st, 2025
Last Modified: December 2nd, 2025
Added to House: July 22nd, 2026

CVSS Vectors

Weaknesses (CWE)

CWE-20 CWE-915

MITRE ATT&CK TTPs

T1190 Exploit Public-Facing Application
Initial Access
T1059 Command and Scripting Interpreter
Execution
T1068 Exploitation for Privilege Escalation
Privilege Escalation
T1213 Data from Information Repositories
Collection
T1565.002 Stored Data Manipulation
Impact