Vulnerability · Published Sep 28, 2026 · Assigned by GitHub_M
CVE-2026-100370DOMSanitizer - Incomplete data: URL Sanitization in DOMSanitizer::isDangerousUrl() Allows Base64-Encoded Payloads to Bypass href and xlink:href Validation
Medium 4.7
In plain English
A medium-severity improper input validation in dom-sanitizer from rhukster. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 20% of all known vulnerabilities).
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| rhukster | dom-sanitizer | < 1.0.15 |
Weakness: CWE-20 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N
References
- https://github.com/rhukster/dom-sanitizer/security/advisories/GHSA-wcj2-r6vg-rm97 x_refsource_CONFIRM
- https://github.com/rhukster/dom-sanitizer/commit/10f97807e4501d60f63987f2e76a38cdbf312dcb x_refsource_MISC
- https://github.com/rhukster/dom-sanitizer/commit/fb8f758b41134fc5fb2f563666f2330c69e31f94 x_refsource_MISC
- https://github.com/rhukster/dom-sanitizer/releases/tag/1.0.15 x_refsource_MISC