Low [CVE-2026-73491] Cross-Site Scripting via malformed `javascript:` URI parsing
This low-severity Red Hat Linux advisory covers CVE-2026-73491.
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Summary
Loofah is a general library for manipulating and transforming HTML/XML documents and fragments, built on top of Nokogiri. From 2.25.0 until 2.25.2, Loofah::HTML5::Scrub.allowed_uri? does not reject javascript: URIs whose scheme is split or prefixed with the HTML5 named whitespace character references or
CGI.unescapeHTML leaves those references intact, so allowed_uri? reports the URL safe even though a browser decodes and strips the tab or line feed and executes the resulting javascript: URL. This issue affects only callers that pass HTML-encoded strings directly to allowed_uri?; Loofah's default sanitize() path is not affected.
This issue is fixed in version 2.25.2. A flaw was found in Loofah.
This vulnerability allows a remote attacker to craft a malicious URI that, when processed by affected callers, is incorrectly deemed safe. Consequently, a web browser will decode and execute the embedded JavaScript code, leading to Cross-Site Scripting (XSS) and potential arbitrary code execution in the user's browser context.
Red Hat severity: Low — CVSS 3.7 (CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:N). Weakness: CWE-1289.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 3 hours ago·verify at source
Mitigation
Upgrade to a fixed release: 2.25.2. That is the remediation for this advisory.
The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.
Official advisory · high-confidence parse· fetched 3 hours ago·verify at source
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