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Fencer Intel
medium 5.3

CVE-2025-66400 json

mdast-util-to-hast unsanitized class attribute

published 11mo ago modified 22d ago also GHSA-4fh9-h7wg-q85m , EUVD-2025-200113

cvss
5.3
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 25%
public exploits
0
none known

Summary

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.

Patch / fix

  • npm mdast-util-to-hast 13.2.1
  • unifiedjs mdast-util-to-hast 13.2.1

Is CVE-2025-66400 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-66400 updated cvss 5.3

mdast-util-to-hast: mdast-util-to-hast: Markdown code elements can appear as regular page content

  • Red Hat Gatekeeper 3 gatekeeper/gatekeeper-rhel9 Red Hat Migration Toolkit for Applications 7 mta/mta-ui-rhel9 Red Hat Migration Toolkit for Applications 8 mta/mta-ui-rhel9 Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-console-plugin-rhel9, openshift-lightspeed/lightspeed-console-plugin-pf5-rhel9 Red Hat OpenShift Pipelines openshift-pipelines/pipelines-hub-ui-rhel8, openshift-pipelines/pipelines-hub-ui-rhel9, openshift-pipelines/pipelines-hub-api-rhel8, openshift-pipelines/pipelines-hub-api-rhel9, openshift-pipelines/pipelines-hub-db-migration-rhel8, openshift-pipelines/pipelines-hub-db-migration-rhel9 Red Hat Ansible Automation Platform 2 automation-hub, python-galaxy-ng, automation-gateway, python3x-galaxy-ng, python3.11-galaxy-ng, automation-platform-ui, +2 more
    +9 more products
    Red Hat build of Apache Camel - HawtIO 4 io.hawt-project Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9 Red Hat JBoss Enterprise Application Platform 8 org.keycloak-keycloak-parent Red Hat JBoss Enterprise Application Platform Expansion Pack org.keycloak-keycloak-parent Red Hat OpenShift AI (RHOAI) rhoai/odh-dashboard-rhel9, rhoai/odh-mod-arch-gen-ai-rhel9, rhoai/odh-mod-arch-model-registry-rhel9 Red Hat OpenShift Container Platform 4 openshift4/ose-agent-installer-ui-rhel9 Red Hat Quay 3 quay/quay-rhel8 Red Hat Satellite 6 satellite/iop-advisor-frontend-rhel9 Red Hat Trusted Profile Analyzer rhtpa/rhtpa-trustification-service-rhel9
    affected: workaround, no fix available “Fix deferred”

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
11mo ago

Exploit prediction

0.33% chance of exploitation in the next 30 days, higher than 25% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 4.0 6.9 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
CNA 4.0 6.9 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
GitHub 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Affected packages

ecosystem package affected fixed in
npm mdast-util-to-hast
>=13.0.0, <13.2.1
13.2.1

Affected products

  • syntax-tree mdast-util-to-hast

Classification

Weakness
  • CWE-20 Improper Input Validation
  • CWE-915 Improperly Controlled Modification of Dynamically-Determined Object Attributes

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.