Vulnerability Database

365,542

Total vulnerabilities in the database

Loofah: SVG `href` attribute bypasses local-reference restriction — loofah

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

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.

  • Published: Jul 21, 2026
  • Updated: Jul 22, 2026
  • GHSA: GHSA-9wjq-cp2p-hrgf
  • Severity: Medium
  • Exploit:
  • CISA KEV:

CVSS v3:

  • Severity: Low
  • Score: 4.7
  • AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N

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