CVE-2026-66010: DOMPurify before 3.4.12 fails to execute afterSanitizeElements hook for custom elements allowed via CUSTOM_ELE

Q: How do I fix CVE-2026-66010?

dompurify: upgrade to 3.4.12. Exact commands for each OS are on this page.

Q: Is CVE-2026-66010 being exploited?

CVE-2026-66010 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-66010 affect?

CVE-2026-66010 affects dompurify. Severity is medium (CVSS 6.1). DOMPurify before 3.4.12 fails to execute afterSanitizeElements hook for custom elements allowed via CUSTOM_ELEMENT_HANDLING.tagNameCheck, allowing attributes to bypass application security policies. Attackers can preserve sensitive attribut

Q: How urgent is CVE-2026-66010?

Priority 29/100. Public exploit reference

Routine

MEDIUM 6.1UPGRADE

CVE-2026-66010 is a medium-severity flaw (CVSS 6.1) affecting dompurify. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

DOMPurify before 3.4.12 fails to execute afterSanitizeElements hook for custom elements allowed via CUSTOM_ELEMENT_HANDLING.tagNameCheck, allowing attributes to bypass application security policies. Attackers can preserve sensitive attributes on custom elements that later re-inject them into innerHTML sinks, creating second-order XSS gadgets.

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.2% (top 89%)
CISA exploited list	No
Weakness	CWE-79
Published	2026-07-24
Last modified	2026-10-24

Publisher (CNA): VulnCheck · Vendor: cure53

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-24 13:18 UTCPublished CVE record published
2026-10-24 13:10 UTCUpdated Record last modified

cure53 dompurify UPGRADE

Affected: < 3.4.12

Fixed in: 3.4.12

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy dompurify || rpm -q dompurify || dompurify --version

2. UPGRADE to 3.4.12 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade dompurify

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade dompurify

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-66010?

dompurify: upgrade to 3.4.12. Exact commands for each OS are on this page.

Is CVE-2026-66010 being exploited?

CVE-2026-66010 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-66010 affect?

CVE-2026-66010 affects dompurify. Severity is medium (CVSS 6.1). DOMPurify before 3.4.12 fails to execute afterSanitizeElements hook for custom elements allowed via CUSTOM_ELEMENT_HANDLING.tagNameCheck, allowing attributes to bypass application security policies. Attackers can preserve sensitive attribut

How urgent is CVE-2026-66010?

Priority 29/100. Public exploit reference

Related CVEs

CVE-2026-65898 HIGH 7.2 UPGRADE DOMPurify before 3.4.11 fails to clone the ALLOWED_ATTR allowlist when setConfig() is used with an uponSanitiz
CVE-2026-65899 MEDIUM 6.1 UPGRADE DOMPurify 3.0.0 before 3.4.9 does not reset the retained Trusted Types policy when clearConfig() is called, so
CVE-2026-65902 MEDIUM 6.1 UPGRADE DOMPurify before 3.4.7 (affected versions <= 3.4.5) passes direct references to the module-level DEFAULT_ALLOW
CVE-2026-65911 MEDIUM 6.1 UPGRADE In DOMPurify through 3.3.3, function predicates supplied via ADD_ATTR or ADD_TAGS to DOMPurify.sanitize() pers
CVE-2026-65900 MEDIUM 6.1 UPGRADE DOMPurify versions >=3.0.0 and before 3.4.8, when configured with SAFE_FOR_TEMPLATES together with a DOM outpu

References

← Back to latest CVEs