CVE-2026-100370: CWE-20: Improper Input Validation in rhukster dom-sanitizer
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.
AI Analysis
Technical Summary
The vulnerability in rhukster dom-sanitizer versions before 1.0.15 lies in the isDangerousUrl() method, which attempts to block dangerous URL schemes in href and xlink:href attributes. While it correctly rejects the javascript: scheme, it only rejects data: URLs if the literal substring 'onload' appears. Because data: payloads are often Base64-encoded, dangerous content such as <script> tags or event handlers can evade detection and remain in sanitized output. This represents an incomplete input validation and sanitization flaw. The issue was addressed and patched in version 1.0.15.
Potential Impact
This vulnerability allows potentially unsafe data: URLs with encoded active content to bypass the sanitizer's checks, which could lead to injection of active markup in sanitized DOM/SVG/MathML content. The CVSS score of 4.7 (medium severity) reflects limited impact with user interaction required and no direct integrity or availability impact. There are no known exploits in the wild.
Mitigation Recommendations
Upgrade to rhukster dom-sanitizer version 1.0.15 or later, where this input validation flaw in isDangerousUrl() has been fixed. No other mitigation is required as the patch fully addresses the issue.
CVE-2026-100370: CWE-20: Improper Input Validation in rhukster dom-sanitizer
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.
CVSS v3.1
Score 4.7medium
Affected software
rhukster
dom-sanitizer
pkg:github/rhukster/dom-sanitizerRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in rhukster dom-sanitizer versions before 1.0.15 lies in the isDangerousUrl() method, which attempts to block dangerous URL schemes in href and xlink:href attributes. While it correctly rejects the javascript: scheme, it only rejects data: URLs if the literal substring 'onload' appears. Because data: payloads are often Base64-encoded, dangerous content such as <script> tags or event handlers can evade detection and remain in sanitized output. This represents an incomplete input validation and sanitization flaw. The issue was addressed and patched in version 1.0.15.
Potential Impact
This vulnerability allows potentially unsafe data: URLs with encoded active content to bypass the sanitizer's checks, which could lead to injection of active markup in sanitized DOM/SVG/MathML content. The CVSS score of 4.7 (medium severity) reflects limited impact with user interaction required and no direct integrity or availability impact. There are no known exploits in the wild.
Mitigation Recommendations
Upgrade to rhukster dom-sanitizer version 1.0.15 or later, where this input validation flaw in isDangerousUrl() has been fixed. No other mitigation is required as the patch fully addresses the issue.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-09-25T19:19:54.699Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6abacf14f7a7c541062b9a4b
Added to database: 09/28/2026, 20:33:24 UTC
Last enriched: 09/28/2026, 20:48:21 UTC
Last updated: 09/29/2026, 03:33:28 UTC
Views: 9
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