Bug 2572750 (CVE-2026-126203) - CVE-2026-126203 loofah: loofah: Cross-site scripting via unescaped attribute values in HTML5 sanitization
Summary: CVE-2026-126203 loofah: loofah: Cross-site scripting via unescaped attribute ...
Keywords:
Status: NEW
Alias: CVE-2026-126203
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-11-12 18:52 UTC by OSIDB Bzimport
Modified: 2026-11-12 19:04 UTC (History)
20 users (show)

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Description OSIDB Bzimport 2026-11-12 18:52:00 UTC 
Loofah is a general library for manipulating and transforming HTML/XML documents and fragments, built on top of Nokogiri. From 2.21.0 until 2.25.3, Loofah's HTML5 APIs Loofah.html5_fragment, Loofah.html5_document, and the scrub_html5_* methods can emit sanitized output that a browser reparses as different markup when used with Nokogiri before 1.19.5, because those Nokogiri versions do not escape angle brackets in attribute values. MathML can place markup inside an allowed attribute so the reparsed output becomes live HTML. The :strip scrubber is affected in every browser, while :prune and :escape are affected in WebKit browsers. Loofah's HTML4 APIs, Loofah::Helpers.sanitize, :whitewash, rails-html-sanitizer's default configuration, and JRuby are not affected. This issue is fixed in version 2.25.3.
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