CVE-2026-126208 (CVSS 4.7)

Description

Loofah is a general library for manipulating and transforming HTML/XML documents and fragments, built on top of Nokogiri. Prior to 2.25.3, Loofah's SVG_ALLOW_LOCAL_HREF safelist lists textPath with lowercase spelling that does not match the HTML5 parser's element name and omits mpath, so external href and xlink:href values on those elements survive sanitization. Firefox fetches the attacker-chosen URL when a viewer renders the content, which can disclose the viewer's IP address, user agent, referrer, and access to hosts routable only from the viewer's network. Chrome and WebKit do not fetch these references, and the impact is a network request rather than script execution. The rails-html-sanitizer PermitScrubber reuses the affected safelist when SVG elements are permitted. This issue is fixed in version 2.25.3.

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CVSS v3.1 Score

4.7

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N

Weakness Type (CWE)

CWE-178 CWE-178

CWE-184 CWE-184

References

Other References

https://github.com/flavorjones/loofah/commit/cdd6ff7fb51998eb181bd2da925ddbcfcc8a3b96 https://github.com/flavorjones/loofah/pull/324 https://github.com/flavorjones/loofah/releases/tag/v2.25.3 https://github.com/flavorjones/loofah/security/advisories/GHSA-345x-3rq2-jfrm

Frequently Asked Questions

What is CVE-2026-126208? +

Loofah is a general library for manipulating and transforming HTML/XML documents and fragments, built on top of Nokogiri. Prior to 2.25.3, Loofah's SVG_ALLOW_LOCAL_HREF safelist lists textPath with lowercase spelling that does not match the HTML5 parser's element name and omits mpath, so external href and xlink:href values on those elements survive sanitization. Firefox fetches the attacker-chosen URL when a viewer renders the content, which can disclose the viewer's IP address, user agent, referrer, and access to hosts routable only from the viewer's network. Chrome and WebKit do not fetch these references, and the impact is a network request rather than script execution. The rails-html-sanitizer PermitScrubber reuses the affected safelist when SVG elements are permitted. This issue is fixed in version 2.25.3. It has a CVSS v3.1 base score of 4.7 (MEDIUM).

How severe is CVE-2026-126208? +

CVE-2026-126208 has a CVSS v3.1 score of 4.7 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

How do I check if I'm vulnerable to CVE-2026-126208? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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