CVE-2026-65904: dompurify — Exploit

Description

DOMPurify through 3.3.3 fails to sanitize DOM elements passed via IN_PLACE mode when the element originates from a different window/realm (e.g., an iframe's contentDocument). A cross-realm instanceof check in the private _isNode() function returns false for foreign-realm nodes, causing DOMPurify to stringify the element (yielding '[object HTMLDivElement]'), silently reset IN_PLACE to false, and return the unsanitized element unchanged with any XSS payloads intact.

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CVSS v3.1 Score

4.7

MEDIUM

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

EPSS — Exploit Prediction

0.0017

Probability of exploitation

0.06%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-754 CWE-754

Affected Products

Vendor	Product	Versions
cure53	dompurify	< 3.4.4

References

Exploits

https://github.com/cure53/DOMPurify/security/advisories/GHSA-4w3q-35jp-p934 https://github.com/cure53/DOMPurify/security/advisories/GHSA-4w3q-35jp-p934

Other References

https://www.vulncheck.com/advisories/dompurify-before-cross-site-scripting-via-in-place-mode

Frequently Asked Questions

What is CVE-2026-65904? +

DOMPurify through 3.3.3 fails to sanitize DOM elements passed via IN_PLACE mode when the element originates from a different window/realm (e.g., an iframe's contentDocument). A cross-realm instanceof check in the private _isNode() function returns false for foreign-realm nodes, causing DOMPurify to stringify the element (yielding '[object HTMLDivElement]'), silently reset IN_PLACE to false, and return the unsanitized element unchanged with any XSS payloads intact. It has a CVSS v3.1 base score of 4.7 (MEDIUM).

How severe is CVE-2026-65904? +

CVE-2026-65904 has a CVSS v3.1 score of 4.7 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0017, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-65904? +

CVE-2026-65904 affects products from cure53, specifically: dompurify. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-65904? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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