flavorjones Loofah up to 2.25.2 HTML5 APIs HTML injection

Summaryinfo

A vulnerability classified as problematic was found in flavorjones Loofah up to 2.25.2. This impacts the function Loofah.html5_fragment/Loofah.html5_document/scrub_html5_* of the component HTML5 APIs. Such manipulation leads to HTML injection. This vulnerability is listed as CVE-2026-126203. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in flavorjones Loofah up to 2.25.2 and classified as problematic. Affected by this issue is the function Loofah.html5_fragment/Loofah.html5_document/scrub_html5_* of the component HTML5 APIs. The manipulation with an unknown input leads to a html injection vulnerability. Using CWE to declare the problem leads to CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Impacted is integrity. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is handled as CVE-2026-126203 since 11/10/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Successful exploitation requires user interaction by the victim. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1059.007 by the MITRE ATT&CK project.

Upgrading to version 2.25.3 eliminates this vulnerability.

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Productinfo

Vendor

• flavorjones

Name

• Loofah

Version

• 2.25.0
• 2.25.1
• 2.25.2

Website

• Product: https://github.com/flavorjones/loofah/

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