CVE-2026-100370 Cross-site scripting in dom-sanitizer
Attackers can bypass URL sanitization using Base64-encoded data URLs to inject malicious scripts, leading to cross-site scripting attacks.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-100370?
CVE-2026-100370 is a medium-severity cross-site scripting vulnerability in rhukster dom-sanitizer, published on 28 Sep 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
DOMSanitizer is a DOM/SVG/MathML Sanitizer for PHP 7.3+. Prior to version 1.0.15, the isDangerousUrl() method is responsible for rejecting dangerous URL values in the href and xlink:href attributes. The weakness is that "javascript:" is rejected as a scheme, while "data:" is rejected only when the literal substring onload appears in the URL value (/^data:.*onload/i). Because data: payloads are routinely Base64-encoded, the dangerous content (<script>, event handlers, etc.) is invisible to that substring test. A URL such as data:text/html;base64,… therefore survives in href / xlink:href, even though the decoded payload is active markup. This is an incomplete input-validation / sanitization defect in the sanitizer itself. This issue has been patched in version 1.0.15.
Weakness: CWE-20
Which versions are affected by CVE-2026-100370?
How do I fix CVE-2026-100370?
No fix has been published for CVE-2026-100370 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-100370 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-100370 exists.
Sources
Also known as GHSA-wcj2-r6vg-rm97.