CVE-2026-73490: Loofah SVG `href` Attribute Bypasses Local-reference Vulnerability

MODERATE
Advisory Identifier: GHSA-9wjq-cp2p-hrgf
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CVSS 4.7
CWE-79
Published
Advisory Summary

CVE-2026-73490 is a MODERATE (CVSS 4.7) svg `href` attribute bypasses local-reference vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Loofah libraries in the RubyGems ecosystem. The issue involves svg `href` attribute bypasses local-reference restriction. Remediation is available by upgrading affected packages to version 2.25.2.

CVE-2026-73490 at a Glance

CVE Identifier CVE-2026-73490
GHSA Identifier GHSA-9wjq-cp2p-hrgf
Severity MODERATE
CVSS v3.1 Base Score 4.7
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product Loofah
Package Ecosystem RubyGems
Published Date
Last Updated

Security Impact

CVSS: 4.7

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction Required (UI:R)
Scope Changed (S:C)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-73490

To remediate this vulnerability, upgrade all affected Loofah dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

loofah fixed: 2.25.2 
Upgrade loofah to 2.25.2
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for loofah

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-73490, inspect your project dependencies for Loofah:

inspect dependencies for loofah

Analyze the terminal output to locate any version of Loofah in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.25.2), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), where 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. In Loofah, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

## 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.

CVE-2026-73490 Affected Loofah Versions

1 component(s)
Fixed Versions:
2.25.2
Product / Package Ecosystem Affected Versions Fixed Version
loofah
gem/loofah
RubyGems
< 2.25.2
2.25.2

References

GitHub Advisory / Wiki ADVISORY
https://github.com/flavorjones/loofah/security/advisories/GHSA-9wjq-cp2p-hrgf
Security Fix Commit FIX COMMIT
https://github.com/flavorjones/loofah/commit/20867b9be689521887364b74822c41ef830523c9
Loofah Source Repository REPOSITORY
https://github.com/flavorjones/loofah
Loofah Release RELEASE
https://github.com/flavorjones/loofah/releases/tag/v2.25.2

Frequently Asked Questions

What is CVE-2026-73490?
CVE-2026-73490 is a security vulnerability in Loofah involving SVG `href` attribute bypasses local-reference restriction under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which Loofah versions are affected?
Affected versions include releases prior to 2.25.2 across affected packages: loofah.
What version fixes CVE-2026-73490?
Upgrading to 2.25.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is loofah affected?
Yes, loofah is affected in releases prior to 2.25.2. Upgrade your dependency to 2.25.2 or later.
What is the CVSS score of CVE-2026-73490?
CVE-2026-73490 has a CVSS v3.1 base score of 4.7 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N.
What CWE is associated with CVE-2026-73490?
CVE-2026-73490 is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (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.).
How can I check RubyGems dependencies for CVE-2026-73490?
Run the dependency tree command: 'inspect dependencies for loofah'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-9wjq-cp2p-hrgf",
  "modified" : "2026-08-12T20:58:17Z",
  "published" : "2026-07-21T22:01:58Z",
  "aliases" : [ "CVE-2026-73490" ],
  "summary" : "Loofah: SVG `href` attribute bypasses local-reference restriction",
  "details" : "## Summary\n\nLoofah'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.\n\n## Impact\n\nSVG `<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.\n\nApplications that sanitize user-supplied SVG (directly, or as part of HTML) with Loofah's default allowlist are affected.\n\n## Mitigation\n\nUpgrade to Loofah >= 2.25.2.\n\n## Credit\n\nFound by the maintainer, Mike Dalessio, during a security audit.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "RubyGems",
      "name" : "loofah"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.25.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/flavorjones/loofah/security/advisories/GHSA-9wjq-cp2p-hrgf"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/flavorjones/loofah/commit/20867b9be689521887364b74822c41ef830523c9"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/flavorjones/loofah"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/flavorjones/loofah/releases/tag/v2.25.2"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-21T22:01:58Z",
    "nvd_published_at" : null
  }
}