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.

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Fixes

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History

Mon, 28 Sep 2026 21:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Mon, 28 Sep 2026 20:30:00 +0000

Type Values Removed Values Added
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.
Title DOMSanitizer - Incomplete data: URL Sanitization in DOMSanitizer::isDangerousUrl() Allows Base64-Encoded Payloads to Bypass href and xlink:href Validation
Weaknesses CWE-20
References
Metrics cvssV3_1

{'score': 4.7, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-09-28T20:40:03.613Z

Reserved: 2026-09-25T19:19:54.699Z

Link: CVE-2026-100370

cve-icon Vulnrichment

Updated: 2026-09-28T20:39:43.065Z

cve-icon NVD

Status : Received

Published: 2026-09-28T21:17:10.280

Modified: 2026-09-28T21:17:10.280

Link: CVE-2026-100370

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-28T21:30:07Z

Weaknesses