ghsa-5qhf-9phg-95m2

{
  "affected": [
    {
      "database_specific": {
        "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-5qhf-9phg-95m2/GHSA-5qhf-9phg-95m2.json"
      },
      "package": {
        "ecosystem": "RubyGems",
        "name": "loofah",
        "purl": "pkg:gem/loofah"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.25.0"
            },
            {
              "fixed": "2.25.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.25.0",
        "2.25.1"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-73492"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-184",
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-21T22:03:11Z",
    "nvd_published_at": null,
    "severity": "LOW"
  },
  "details": "## Summary\n\n`Loofah::HTML5::Scrub.allowed_uri?` does not correctly reject `javascript:` or `vbscript:` URIs when the scheme is split by a numeric character reference that has no trailing semicolon. A browser decodes such references and resolves the URL to an executable `javascript:` scheme, while `allowed_uri?` reports it safe.\n\nThis is a bypass of the fix for [GHSA-46fp-8f5p-pf2m](https://github.com/flavorjones/loofah/security/advisories/GHSA-46fp-8f5p-pf2m), which handled numeric character references with a trailing `;` (`	`, `
`, `
`) but did not cover the forms without semicolons.\n\n## Details\n\n`allowed_uri?` decodes HTML entities with `CGI.unescapeHTML`, which decodes numeric character references only when they carry a trailing `;`. A reference without a semicolon such as `&#58` (colon) or `&#9` (tab) is left literal, so the scheme-detection check finds no scheme, and the method falls through to its scheme-less path and returns `true`.\n\nA browser, however, decodes numeric character references even without a trailing semicolon. An encoded colon such as `&#58` becomes the `:` scheme separator, so `javascript&#58alert(1)` resolves to `javascript:alert(1)`. Encoded whitespace such as `&#9` (tab) is decoded and then stripped from the URL, rejoining the surrounding text, so `java&#9script:alert(1)` also resolves to `javascript:alert(1)`. In both cases the URL executes while `allowed_uri?` approved it as safe.\n\nNote that Loofah's default `sanitize()` path is **not** affected, because Nokogiri decodes or entity-escapes HTML entities during parsing before Loofah evaluates the URI protocol. This issue only affects callers of the public `allowed_uri?` string-level helper that pass it HTML-encoded strings.\n\n## Impact\n\nCallers that validate a user-controlled URL with `Loofah::HTML5::Scrub.allowed_uri?` and then render the approved value into an `href` or other browser-interpreted URI attribute may be vulnerable to cross-site scripting (XSS). This includes applications that call `allowed_uri?` directly, as well as higher-level features built on top of it, such as Action Text 8.2's markdown link validation.\n\n## Mitigation\n\nUpgrade to Loofah >= 2.25.2.\n\n## Credit\n\nResponsibly reported by GitHub user @MoonFuji.",
  "id": "GHSA-5qhf-9phg-95m2",
  "modified": "2026-09-10T03:51:10.544951806Z",
  "published": "2026-07-21T22:03:11Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/flavorjones/loofah/security/advisories/GHSA-5qhf-9phg-95m2"
    },
    {
      "type": "WEB",
      "url": "https://github.com/flavorjones/loofah/commit/f1be9d893b5a8dd79240441a912d8897e74c38c0"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/flavorjones/loofah"
    },
    {
      "type": "WEB",
      "url": "https://github.com/flavorjones/loofah/releases/tag/v2.25.2"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Loofah `allowed_uri?` does not detect `javascript:` URIs split by numeric character references without semicolons"
}