CVE intelligence

CVE-2026-126203

Vulnerability intelligence

Published Nov 12, 2026Sources checked Nov 12, 2026

6.1MEDIUMCVSS out of 10

What this means

Review the available evidence

CVE-2026-126203 and is rated Medium severity with a CVSS score of 6.1. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Microsoft Security Response Center guidance

Vendor revision: Nov 13, 2026

Release Notes

CISA KEVNot listedBased on the latest collected catalog

EPSSUnavailableNo current score collected

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is CVE-2026-126203?

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.

Source: NVD