CVE-2026-73490 is a medium-severity (CVSS 4.7) Cross-site Scripting (XSS) vulnerability in loofah. A fix is available for loofah — see the affected versions and patch details below.
Loofah: SVG `href` attribute bypasses local-reference restriction
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-73490.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-73490 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 384,993 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
loofahReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
Summary
Loofah's HTML5 sanitizer restricted only the xlink:href attribute on certain SVG elements to local, same-document references. Browsers also accept a plain href attribute as an alternative to the deprecated xlink:href per the SVG 2 spec, but Loofah did not apply the same restriction to it, allowing those elements to reference arbitrary external documents.
Impact
SVG <use> can load and render external SVG content by reference. If the referenced external SVG is same-origin and contains scripts or other dangerous content, it could execute in the context of the sanitized document. <feImage> can load external images, which can be used for tracking. Modern browsers restrict cross-origin <use> fetches, which limits but does not eliminate the risk.
Applications that sanitize user-supplied SVG (directly, or as part of HTML) with Loofah's default allowlist are affected.
Mitigation
Upgrade to Loofah >= 2.25.2.
Credit
Found by the maintainer, Mike Dalessio, during a security audit.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | loofah | all versions | 2.25.2bundle update loofah --conservative |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for loofah, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update loofah to 2.25.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-73490 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
A flaw was found in loofah. Loofah is a general library for manipulating and transforming HTML/XML documents and fragments, built on top of Nokogiri. Prior to 2.25.2, Loofah's HTML5 sanitizer applies its local-reference restriction only to the xlink:href attribute on SVG use and feImage elements, while browsers also…
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.Source: Red Hat security advisory for CVE-2026-73490 (CC BY 4.0)
Frequently Asked Questions
Is CVE-2026-73490 in your dependencies?
Find it across RubyGems, including transitive dependencies.