6.9

CVSS Score

4.0

-

CVSS Score

Basic Information

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CVE-2025-66400

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

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.

(GitHub Advisory)

Miggo Vulnerability Database

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CVE-2025-66400

CVE-2025-66400:

6.9

CVSS Score

4.0

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
mdast-util-to-hast	npm	>= 13.0.0, < 13.2.1	13.2.1

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The analysis of the provided patches clearly indicates that the vulnerability lies within the code function in the lib/handlers/code.js file. The commit that introduced the bug (6fc783ae) removed the logic that sanitized the node.lang property, instead using the raw value to construct the className. The fixing commit (ab3a7957) re-introduced sanitization by splitting the node.lang string by whitespace and only using the first resulting token. This prevents the injection of additional class names through character-encoded spaces. Therefore, the code function is the precise location of the vulnerability, as it is responsible for processing the user-controlled lang attribute and generating the vulnerable HTML.

Vulnerable functions

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Vulnerability Intelligence
Miggo AI

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WAF Protection Rules

WAF Rule

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Reasoning

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