{"id":"CVE-2026-126209","aliases":["EUVD-2026-124716","GHSA-p9wj-w8xq-vjx6","UBUNTU-CVE-2026-126209"],"status":"published","title":"Loofah allowed_uri? treats javascript\u0026#x3a alert(1) as safe","description":"Loofah is a general library for manipulating and transforming HTML/XML documents and fragments, built on top of Nokogiri. From 2.25.0 until 2.25.3, Loofah::HTML5::Scrub.allowed_uri? strips whitespace and control characters before decoding a semicolon-less numeric character reference, changing where the reference ends and hiding a javascript: or vbscript: scheme that a browser reconstructs. The bypass applies to encoded colons and encoded scheme letters when a stripped character terminates the numeric reference. An application that renders the approved value in href or another browser-interpreted URI attribute can allow cross-site scripting, and Rails::HTML::Sanitizer.allowed_uri? re-exports the affected helper. Loofah's default sanitize() path is not affected because Nokogiri decodes entities before URI evaluation. This issue is fixed in version 2.25.3.","severity":{"version":"4.0","score":5.3,"vector":"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","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-13","score":0.00414,"percentile":0.36224,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-184","CWE-79"],"published":"2026-11-12T21:01:58Z","modified":"2026-11-13T21:05:25Z","fixes":[{"ecosystem":"RubyGems","package":"loofah","fixed_in":["2.25.3"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"RubyGems","package":"loofah","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.25.0"},{"fixed":"2.25.3"}]}]},{"source":"osv","ecosystem":"RubyGems","package":"loofah","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.25.0"},{"fixed":"2.25.3"}]}],"versions":["2.25.0","2.25.1","2.25.2"]},{"source":"osv","ecosystem":"Ubuntu:16.04:LTS","package":"ruby-loofah","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.2-1","2.0.3-1","2.0.3-2","2.0.3-2+deb9u1build0.16.04.1","2.0.3-2+deb9u2build0.16.04.1","2.0.3-2+deb9u3build0.16.04.1"]},{"source":"osv","ecosystem":"Ubuntu:18.04:LTS","package":"ruby-loofah","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.3-2","2.2.2-1"]},{"source":"osv","ecosystem":"Ubuntu:20.04:LTS","package":"ruby-loofah","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.2.3-1","2.3.1+dfsg-1","2.4.0+dfsg-1"]},{"source":"osv","ecosystem":"Ubuntu:22.04:LTS","package":"ruby-loofah","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.12.0-1","2.13.0-1","2.13.0-2"]},{"source":"osv","ecosystem":"Ubuntu:24.04:LTS","package":"ruby-loofah","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.21.3-1","2.21.4-1","2.22.0-1"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"ruby-loofah","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.25.0-1","2.25.1-2","2.25.2-1"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"ruby-loofah","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.24.1-1","2.25.0-1"]}],"products":[{"vendor":"flavorjones","product":"loofah"}],"references":[{"url":"https://github.com/flavorjones/loofah/security/advisories/GHSA-p9wj-w8xq-vjx6","tags":["x_refsource_CONFIRM","advisory","web","report"]},{"url":"https://github.com/flavorjones/loofah/pull/324","tags":["x_refsource_MISC","fix","web","report"]},{"url":"https://github.com/flavorjones/loofah/commit/62c04841e8252a1b5373afcd2b89fb9b8279e317","tags":["x_refsource_MISC","fix","web","report"]},{"url":"https://github.com/flavorjones/loofah/releases/tag/v2.25.3","tags":["x_refsource_MISC","web","report"]},{"url":"https://github.com/rubysec/ruby-advisory-db/blob/master/gems/loofah/GHSA-p9wj-w8xq-vjx6.yml","tags":["web"]},{"url":"https://github.com/advisories/GHSA-p9wj-w8xq-vjx6"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/126xxx/CVE-2026-126209.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-126209","tags":["advisory"]},{"url":"https://github.com/flavorjones/loofah","tags":["package"]},{"url":"https://ubuntu.com/security/CVE-2026-126209","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-126209","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-126209","title":"Loofah allowed_uri? treats javascript\u0026#x3a alert(1) as safe","description":"Loofah is a general library for manipulating and transforming HTML/XML documents and fragments, built on top of Nokogiri. From 2.25.0 until 2.25.3, Loofah::HTML5::Scrub.allowed_uri? strips whitespace and control characters before decoding a semicolon-less numeric character reference, changing where the reference ends and hiding a javascript: or vbscript: scheme that a browser reconstructs. The bypass applies to encoded colons and encoded scheme letters when a stripped character terminates the numeric reference. An application that renders the approved value in href or another browser-interpreted URI attribute can allow cross-site scripting, and Rails::HTML::Sanitizer.allowed_uri? re-exports the affected helper. Loofah's default sanitize() path is not affected because Nokogiri decodes entities before URI evaluation. This issue is fixed in version 2.25.3.","status":"published","published":"2026-11-12T21:01:58.128Z","modified":"2026-11-12T21:01:58.128Z","cvss":[{"version":"4.0","score":5.3,"vector":"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","level":"medium","assessor":"cna"}],"cwes":["CWE-79","CWE-184"],"updated_at":"2026-11-12T22:49:19.799402Z"}],"euvd":[{"id":"EUVD-2026-124716","description":"Loofah is a general library for manipulating and transforming HTML/XML documents and fragments, built on top of Nokogiri. From 2.25.0 until 2.25.3, Loofah::HTML5::Scrub.allowed_uri? strips whitespace and control characters before decoding a semicolon-less numeric character reference, changing where the reference ends and hiding a javascript: or vbscript: scheme that a browser reconstructs. The bypass applies to encoded colons and encoded scheme letters when a stripped character terminates the numeric reference. An application that renders the approved value in href or another browser-interpreted URI attribute can allow cross-site scripting, and Rails::HTML::Sanitizer.allowed_uri? re-exports the affected helper. Loofah's default sanitize() path is not affected because Nokogiri decodes entities before URI evaluation. This issue is fixed in version 2.25.3.","status":"published","published":"2026-11-12T21:01:58Z","modified":"2026-11-12T21:01:58Z","cvss":[{"version":"4.0","score":5.3,"vector":"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","level":"medium"}],"updated_at":"2026-11-12T23:36:13.328131Z"}],"ghsa":[{"id":"GHSA-p9wj-w8xq-vjx6","title":"Loofah allowed_uri? treats javascript\u0026#x3a alert(1) as safe","description":"## 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\u0026#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 `\u0026#x3a alert` decodes as `\u0026#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 `\u0026#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.","status":"published","published":"2026-11-12T21:26:25Z","modified":"2026-11-12T21:27:46Z","cvss":[{"version":"4.0","score":5.3,"vector":"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","level":"medium"}],"cwes":["CWE-79","CWE-184"],"updated_at":"2026-11-12T21:43:33.07162Z"}],"nvd":[{"id":"CVE-2026-126209","description":"Loofah is a general library for manipulating and transforming HTML/XML documents and fragments, built on top of Nokogiri. From 2.25.0 until 2.25.3, Loofah::HTML5::Scrub.allowed_uri? strips whitespace and control characters before decoding a semicolon-less numeric character reference, changing where the reference ends and hiding a javascript: or vbscript: scheme that a browser reconstructs. The bypass applies to encoded colons and encoded scheme letters when a stripped character terminates the numeric reference. An application that renders the approved value in href or another browser-interpreted URI attribute can allow cross-site scripting, and Rails::HTML::Sanitizer.allowed_uri? re-exports the affected helper. Loofah's default sanitize() path is not affected because Nokogiri decodes entities before URI evaluation. This issue is fixed in version 2.25.3.","status":"published","published":"2026-11-12T21:17:22.21Z","modified":"2026-11-12T22:09:39.233Z","cvss":[{"version":"4.0","score":5.3,"vector":"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"medium","assessor":"secondary"}],"cwes":["CWE-79","CWE-184"],"updated_at":"2026-11-12T23:33:09.696019Z"}],"osv":[{"id":"CVE-2026-126209","title":"Loofah allowed_uri? treats javascript\u0026#x3a alert(1) as safe","description":"Loofah is a general library for manipulating and transforming HTML/XML documents and fragments, built on top of Nokogiri. From 2.25.0 until 2.25.3, Loofah::HTML5::Scrub.allowed_uri? strips whitespace and control characters before decoding a semicolon-less numeric character reference, changing where the reference ends and hiding a javascript: or vbscript: scheme that a browser reconstructs. The bypass applies to encoded colons and encoded scheme letters when a stripped character terminates the numeric reference. An application that renders the approved value in href or another browser-interpreted URI attribute can allow cross-site scripting, and Rails::HTML::Sanitizer.allowed_uri? re-exports the affected helper. Loofah's default sanitize() path is not affected because Nokogiri decodes entities before URI evaluation. This issue is fixed in version 2.25.3.","status":"published","published":"2026-11-12T21:01:58.128Z","modified":"2026-11-14T02:47:26.446761187Z","cvss":[{"version":"4.0","score":5.3,"vector":"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","level":"medium"}],"cwes":["CWE-184","CWE-79"],"updated_at":"2026-11-14T03:11:13.096066Z"},{"id":"GHSA-p9wj-w8xq-vjx6","title":"Loofah allowed_uri? treats javascript\u0026#x3a alert(1) as safe","description":"## 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\u0026#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 `\u0026#x3a alert` decodes as `\u0026#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 `\u0026#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.","status":"published","published":"2026-11-12T21:26:25Z","modified":"2026-11-12T21:30:03.002169937Z","cvss":[{"version":"4.0","score":5.3,"vector":"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","level":"medium"}],"cwes":["CWE-184","CWE-79"],"updated_at":"2026-11-12T21:46:08.910323Z"},{"id":"UBUNTU-CVE-2026-126209","description":"Loofah is a general library for manipulating and transforming HTML/XML documents and fragments, built on top of Nokogiri. From 2.25.0 until 2.25.3, Loofah::HTML5::Scrub.allowed_uri? strips whitespace and control characters before decoding a semicolon-less numeric character reference, changing where the reference ends and hiding a javascript: or vbscript: scheme that a browser reconstructs. The bypass applies to encoded colons and encoded scheme letters when a stripped character terminates the numeric reference. An application that renders the approved value in href or another browser-interpreted URI attribute can allow cross-site scripting, and Rails::HTML::Sanitizer.allowed_uri? re-exports the affected helper. Loofah's default sanitize() path is not affected because Nokogiri decodes entities before URI evaluation. This issue is fixed in version 2.25.3.","status":"published","published":"2026-11-13T00:00:00Z","modified":"2026-11-13T21:05:25.361423973Z","cvss":[{"version":"4.0","score":5.3,"vector":"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","level":"medium"}],"updated_at":"2026-11-13T21:30:20.292037Z"}]}}