CVE-2026-0540 in DOMPurify
Summary
by MITRE • 03/03/2026
DOMPurify 3.1.3 through 3.3.1 and 2.5.3 through 2.5.8, fixed in commit 2726c74, contain a cross-site scripting vulnerability that allows attackers to bypass attribute sanitization by exploiting five missing rawtext elements (noscript, xmp, noembed, noframes, iframe) in the SAFE_FOR_XML regex. Attackers can include payloads like </noscript><img src=x onerror=alert(1)> in attribute values to execute JavaScript when sanitized output is placed inside these unprotected rawtext contexts.
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Analysis
by VulDB Data Team • 04/08/2026
CVE-2026-0540 represents a critical cross-site scripting vulnerability affecting DOMPurify versions 2.5.3 through 2.5.8 and 3.1.3 through 3.3.1, with the flaw residing in the library's handling of rawtext elements within its SAFE_FOR_XML regular expression. This vulnerability stems from insufficient sanitization of five specific HTML elements: noscript, xmp, noembed, noframes, and iframe, which are not properly protected against attribute injection attacks. The technical flaw manifests when attackers craft malicious payloads that exploit these unprotected rawtext contexts, allowing them to bypass the intended security measures that should prevent script execution within attribute values. When sanitized output containing these malicious payloads is rendered within the vulnerable rawtext elements, the embedded JavaScript code executes in the victim's browser context, creating a persistent cross-site scripting vector that can be leveraged for session hijacking, data theft, or further exploitation. This vulnerability directly relates to CWE-79, which addresses cross-site scripting flaws, and maps to ATT&CK technique T1203, specifically targeting the exploitation of input validation weaknesses to execute arbitrary code. The operational impact of this vulnerability is significant as it undermines the core security promise of DOMPurify, which is designed to sanitize untrusted HTML content for safe use in web applications. Attackers can craft payloads such as </noscript><img src=x onerror=alert(1)> that appear harmless within attribute values but become active scripts when the sanitized content is rendered inside the affected rawtext elements. The vulnerability's exploitation requires minimal prerequisites, making it particularly dangerous for applications that rely on DOMPurify for content sanitization, especially in environments where user-generated content is processed and displayed. Organizations using affected versions of DOMPurify should immediately upgrade to patched versions, as the vulnerability allows attackers to circumvent security controls that are fundamental to preventing XSS attacks in web applications. The fix implemented in commit 2726c74 addresses the root cause by properly incorporating these five rawtext elements into the sanitization process, ensuring that attribute values are properly escaped or removed when they appear within contexts that could potentially execute JavaScript code. This remediation aligns with industry best practices for HTML sanitization and demonstrates the importance of comprehensive testing for edge cases in security libraries that process user input. The vulnerability also highlights the complexity of HTML parsing and sanitization, where seemingly innocuous elements can create unexpected attack vectors when not properly accounted for in security validation processes.