Is CVE-2025-66400 in the CISA KEV catalog?

No. CVE-2025-66400 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2025-66400?

CVE-2025-66400 has a CVSS v3 base score of 5.3 (MEDIUM).

What is the EPSS score for CVE-2025-66400?

CVE-2025-66400 has an EPSS score of 0.26% (17th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2025-66400?

Upgrade mdast-util-to-hast to 13.2.1 or later.

CVE & CISA-KEV Catalog

CVE-2025-66400

MEDIUM

5.3

CVSS v3

NVD

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.

CWE-20Improper Input Validation CWE-915

How to fix

Remediation Available

mdast-util-to-hastNVD

Affected:>= 13.0.0, < 13.2.1Fixed in:13.2.1CVE-2025-66400derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityLow

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Exploit Intelligence

0.26%probability of exploitation in 30 days

17thpercentile

Low risk: more likely to be exploited than 17% of all known CVEs.

References

Patch2

Vendor Advisory1

github.com

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Markdown

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HTML

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-02-06.