{"id":"GHSA-p9wj-w8xq-vjx6","summary":"Loofah allowed_uri? treats javascript&#x3a alert(1) as safe","details":"## Summary\n\n`Loofah::HTML5::Scrub.allowed_uri?` returns `true` for a `javascript:` or `vbscript:` URI whose scheme is split by a numeric character reference without a trailing semicolon, followed by a character that `allowed_uri?` strips, such as a space or tab. A browser ends the reference at that character and reads `javascript&#x3a alert(1)` as `javascript: alert(1)`.\n\n## Details\n\n`allowed_uri?` strips control characters and whitespace before it decodes numeric character references. Removing the character that ends a semicolon-less reference lets the reference run on into the following text, so `&#x3a alert` decodes as `&#x3aa` (U+03AA) instead of a colon, and no scheme is detected. The same applies to decimal references and to references that encode a scheme letter, as in `&#x6a\\tavascript:alert(1)`.\n\nLoofah's default `sanitize()` path is **not** affected, because Nokogiri decodes the entity during parsing before Loofah evaluates the URI. This issue affects only callers of the public `allowed_uri?` string-level helper that pass it HTML-encoded strings.\n\n## Impact\n\nApplications that validate a user-controlled URL with `Loofah::HTML5::Scrub.allowed_uri?` and then render the approved value into an `href` or another browser-interpreted URI attribute may be vulnerable to cross-site scripting. `Rails::HTML::Sanitizer.allowed_uri?` re-exports the same helper.\n\n## Mitigation\n\nUpgrade to Loofah \u003e= 2.25.3.\n\n## Credit\n\nResponsibly reported by GitHub user @manus-pi.","aliases":["CVE-2026-126209"],"modified":"2026-11-12T21:30:03.002169937Z","published":"2026-11-12T21:26:25Z","database_specific":{"cwe_ids":["CWE-184","CWE-79"],"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2026-11-12T21:26:25Z","nvd_published_at":null},"references":[{"type":"WEB","url":"https://github.com/flavorjones/loofah/security/advisories/GHSA-p9wj-w8xq-vjx6"},{"type":"WEB","url":"https://github.com/flavorjones/loofah/pull/324"},{"type":"WEB","url":"https://github.com/flavorjones/loofah/commit/62c04841e8252a1b5373afcd2b89fb9b8279e317"},{"type":"PACKAGE","url":"https://github.com/flavorjones/loofah"},{"type":"WEB","url":"https://github.com/flavorjones/loofah/releases/tag/v2.25.3"},{"type":"WEB","url":"https://github.com/rubysec/ruby-advisory-db/blob/master/gems/loofah/GHSA-p9wj-w8xq-vjx6.yml"}],"affected":[{"package":{"name":"loofah","ecosystem":"RubyGems","purl":"pkg:gem/loofah"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.25.0"},{"fixed":"2.25.3"}]}],"versions":["2.25.0","2.25.1","2.25.2"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/11/GHSA-p9wj-w8xq-vjx6/GHSA-p9wj-w8xq-vjx6.json"}}],"schema_version":"1.9.2","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N"}]}