CVE-2026-103687 in dom-sanitizer
Summary
by MITRE • 10/01/2026
A vulnerability has been found in rhukster dom-sanitizer up to 1.0.15. The affected element is the function url of the file src/DOMSanitizer.php of the component SVG Sanitization. Such manipulation leads to incomplete blacklist. It is possible to launch the attack remotely. The exploit has been disclosed to the public and may be used. Upgrading to version 1.0.16 is sufficient to fix this issue. The name of the patch is 139c46c3d7c9bc81542b7b5a58d5cde5d0e0195a. Upgrading the affected component is recommended.
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Analysis
by VulDB Data Team • 10/01/2026
The vulnerability identified in rhukster dom-sanitizer versions up to 1.0.15 represents a critical flaw within the SVG sanitization logic, specifically located in the url function of the src/DOMSanitizer.php file. This issue stems from an incomplete blacklist mechanism designed to filter out potentially malicious content during the processing of Scalable Vector Graphics files. The core technical failure lies in the sanitizer's inability to adequately validate or restrict certain URL schemes and protocols when parsing SVG elements that contain external resources. By failing to enforce a comprehensive list of prohibited patterns, the library allows attackers to inject crafted payloads that bypass existing security checks. This deficiency effectively neutralizes the protective measures intended by the sanitization process, leaving applications vulnerable to client-side attacks through malformed or maliciously constructed SVG inputs.
The operational impact of this vulnerability is significant due to its potential for remote exploitation and public availability of proof-of-concept exploits. Attackers can leverage this flaw to execute Cross-Site Scripting (XSS) attacks by embedding JavaScript code within the href attributes of SVG elements, such as <a> or <image>, which are processed through the vulnerable url function. Since many web applications accept user-uploaded images for display purposes, an attacker could upload a maliciously crafted SVG file that triggers script execution in the victim's browser upon viewing. This capability allows for session hijacking, credential theft, defacement of application interfaces, or further pivoting into internal networks if combined with other vulnerabilities. The public disclosure and availability of exploit code significantly lower the barrier to entry for threat actors, increasing the likelihood of automated scanning and targeted attacks against systems still running affected versions.
From a classification perspective, this vulnerability aligns closely with CWE-79, which describes Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting. The specific mechanism involves insufficient validation of user-supplied input that is subsequently rendered in the browser without proper encoding or restriction. Furthermore, within the context of the MITRE ATT&CK framework, this flaw facilitates techniques associated with Client-side Rendering and potentially Command and Control if used to exfiltrate data via beaconing URLs embedded in SVGs. The lack of strict protocol whitelisting allows for the use of javascript: URIs or other dangerous schemes that bypass standard HTTP/HTTPS restrictions, thereby enabling arbitrary code execution within the context of the vulnerable web application.
To mitigate this risk, immediate action is required to upgrade the rhukster dom-sanitizer library to version 1.0.16 or later. The patch associated with commit hash 139c46c3d7c9bc81542b7b5a58d5cde5d0e0195a addresses the incomplete blacklist by enhancing the validation logic within the url function to properly reject dangerous URL schemes and enforce stricter sanitization rules. Organizations relying on this component should verify their dependency trees and update accordingly in all environments, including development, staging, and production systems. Additionally, implementing defense-in-depth strategies such as Content Security Policy headers can provide an additional layer of protection by restricting script execution sources, although reliance solely on CSP is not recommended given the fundamental flaw in the sanitization library itself. Regular security audits and dependency scanning should be integrated into the software development lifecycle to detect similar vulnerabilities in third-party libraries before they are deployed.