{"id":"CVE-2026-66843","aliases":["EEF-CVE-2026-66843","EUVD-2026-54080","GHSA-6g7x-33rf-28v3","GHSA-xmm9-jc22-rcgj"],"status":"published","title":"html_sanitize_ex HTML5 scrubber keeps attacker-supplied `\u003cobject\u003e` elements, allowing untrusted content embedding","description":"Inclusion of Functionality from Untrusted Control Sphere vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows a remote attacker to load a document of their choosing into a trusted page via the data attribute of an \u003cobject\u003e element in sanitized HTML. object is the one URI-bearing element in lib/html_sanitize_ex/scrubber/html5.ex never registered through allow_tag_with_uri_attributes/3, and its only guard is a prefix match on lowercase \"javascript:\", so mixed-case variants, data: URIs, protocol-relative URLs and same-origin paths all survive.\n\nThis is not unconditional cross-site scripting. A javascript: URL does not execute through \u003cobject data\u003e in current browsers, data: documents load in an opaque origin, and host-origin script execution additionally requires the application to serve attacker-controlled content from a same-origin path.\n\nThis issue affects html_sanitize_ex: from 0.3.1 before 1.4.5 and from 1.5.0-rc.0 before 1.5.3.","severity":{"version":"4.0","score":2.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N","level":"low","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.00512,"percentile":0.43989,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-829"],"published":"2026-08-06T14:48:20Z","modified":"2026-10-28T02:31:10Z","fixes":[{"ecosystem":"Hex","package":"html_sanitize_ex","fixed_in":["1.4.5","1.5.3"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Hex","package":"html_sanitize_ex","ranges":[{"type":"SEMVER","events":[{"introduced":"0.3.1"},{"fixed":"1.4.5"}]},{"type":"SEMVER","events":[{"introduced":"1.5.0-rc.0"},{"fixed":"1.5.3"}]}],"versions":["0.3.1","1.0.0","1.0.1","1.1.0","1.1.0-rc1","1.1.1","1.2.0","1.3.0","1.3.0-rc1","1.3.0-rc2","1.3.0-rc3","1.4.0","1.4.1","1.4.2","1.4.3","1.4.4","1.4.4-rc.0","1.5.0","1.5.0-rc.0","1.5.1","1.5.2"]}],"products":[{"vendor":"rrrene","product":"html_sanitize_ex"},{"vendor":"rrrene","product":"htmlsanitizeex"}],"references":[{"url":"https://github.com/rrrene/html_sanitize_ex/security/advisories/GHSA-xmm9-jc22-rcgj","tags":["vendor-advisory","related","Broken Link","advisory"]},{"url":"https://cna.erlef.org/cves/CVE-2026-66843.html","tags":["related","Patch","Third Party Advisory","web"]},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-66843","tags":["related","Patch","Third Party Advisory","web"]},{"url":"https://github.com/rrrene/html_sanitize_ex/commit/bec27fec4de99e40c68c4285a610e09e791a3eaf","tags":["patch","Patch","fix"]},{"url":"https://github.com/rrrene/html_sanitize_ex/commit/ce038aa1af5a960d50f8eb5d368cc57bb2b9a9f0","tags":["patch","fix"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-66843","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-6g7x-33rf-28v3"},{"url":"https://github.com","tags":["web"]},{"url":"https://repo.hex.pm","tags":["web"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/66xxx/CVE-2026-66843.json","tags":["advisory"]},{"url":"https://github.com/rrrene/html_sanitize_ex","tags":["package"]},{"url":"https://hex.pm/packages/html_sanitize_ex","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-66843","title":"html_sanitize_ex HTML5 scrubber keeps attacker-supplied `\u003cobject\u003e` elements, allowing untrusted content embedding","description":"Inclusion of Functionality from Untrusted Control Sphere vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows a remote attacker to load a document of their choosing into a trusted page via the data attribute of an \u003cobject\u003e element in sanitized HTML. object is the one URI-bearing element in lib/html_sanitize_ex/scrubber/html5.ex never registered through allow_tag_with_uri_attributes/3, and its only guard is a prefix match on lowercase \"javascript:\", so mixed-case variants, data: URIs, protocol-relative URLs and same-origin paths all survive.\n\nThis is not unconditional cross-site scripting. A javascript: URL does not execute through \u003cobject data\u003e in current browsers, data: documents load in an opaque origin, and host-origin script execution additionally requires the application to serve attacker-controlled content from a same-origin path.\n\nThis issue affects html_sanitize_ex: from 0.3.1 before 1.4.5 and from 1.5.0-rc.0 before 1.5.3.","status":"published","published":"2026-08-06T14:48:20.513Z","modified":"2026-08-19T11:51:46.161Z","cvss":[{"version":"4.0","score":2.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N","level":"low","assessor":"cna"}],"cwes":["CWE-829"],"updated_at":"2026-11-02T14:20:12.939084Z"}],"euvd":[{"id":"EUVD-2026-54080","description":"Inclusion of Functionality from Untrusted Control Sphere vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows a remote attacker to load a document of their choosing into a trusted page via the data attribute of an \u003cobject\u003e element in sanitized HTML. object is the one URI-bearing element in lib/html_sanitize_ex/scrubber/html5.ex never registered through allow_tag_with_uri_attributes/3, and its only guard is a prefix match on lowercase \"javascript:\", so mixed-case variants, data: URIs, protocol-relative URLs and same-origin paths all survive.\n\nThis is not unconditional cross-site scripting. A javascript: URL does not execute through \u003cobject data\u003e in current browsers, data: documents load in an opaque origin, and host-origin script execution additionally requires the application to serve attacker-controlled content from a same-origin path.\n\nThis issue affects html_sanitize_ex: from 0.3.1 before 1.4.5 and from 1.5.0-rc.0 before 1.5.3.","status":"published","published":"2026-08-06T14:48:20Z","modified":"2026-08-19T11:51:46Z","cvss":[{"version":"4.0","score":2.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N","level":"low"}],"updated_at":"2026-11-02T18:01:45.709762Z"}],"ghsa":[{"id":"GHSA-6g7x-33rf-28v3","title":"Inclusion of Functionality from Untrusted Control Sphere vulnerability in the HTML5 scrubber in...","description":"Inclusion of Functionality from Untrusted Control Sphere vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows a remote attacker to load a document of their choosing into a trusted page via the data attribute of an \u003cobject\u003e element in sanitized HTML. object is the one URI-bearing element in lib/html_sanitize_ex/scrubber/html5.ex never registered through allow_tag_with_uri_attributes/3, and its only guard is a prefix match on lowercase \"javascript:\", so mixed-case variants, data: URIs, protocol-relative URLs and same-origin paths all survive.\n\nThis is not unconditional cross-site scripting. A javascript: URL does not execute through \u003cobject data\u003e in current browsers, data: documents load in an opaque origin, and host-origin script execution additionally requires the application to serve attacker-controlled content from a same-origin path.\n\nThis issue affects html_sanitize_ex: from 0.3.1 before 1.5.3.","status":"published","published":"2026-08-06T18:30:50Z","modified":"2026-08-19T12:32:22Z","cvss":[{"version":"4.0","score":2.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/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":"low"},{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium"}],"cwes":["CWE-829"],"updated_at":"2026-11-02T15:10:38.677871Z"}],"nvd":[{"id":"CVE-2026-66843","description":"Inclusion of Functionality from Untrusted Control Sphere vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows a remote attacker to load a document of their choosing into a trusted page via the data attribute of an \u003cobject\u003e element in sanitized HTML. object is the one URI-bearing element in lib/html_sanitize_ex/scrubber/html5.ex never registered through allow_tag_with_uri_attributes/3, and its only guard is a prefix match on lowercase \"javascript:\", so mixed-case variants, data: URIs, protocol-relative URLs and same-origin paths all survive.\n\nThis is not unconditional cross-site scripting. A javascript: URL does not execute through \u003cobject data\u003e in current browsers, data: documents load in an opaque origin, and host-origin script execution additionally requires the application to serve attacker-controlled content from a same-origin path.\n\nThis issue affects html_sanitize_ex: from 0.3.1 before 1.4.5 and from 1.5.0-rc.0 before 1.5.3.","status":"published","published":"2026-08-06T16:16:49.627Z","modified":"2026-10-24T16:10:00.153Z","cvss":[{"version":"4.0","score":2.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/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":"low","assessor":"secondary"},{"version":"3.1","score":6.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","level":"medium","assessor":"primary"}],"cwes":["CWE-829"],"updated_at":"2026-11-02T14:12:35.386166Z"}],"osv":[{"id":"CVE-2026-66843","title":"html_sanitize_ex HTML5 scrubber keeps attacker-supplied `\u003cobject\u003e` elements, allowing untrusted content embedding","description":"Inclusion of Functionality from Untrusted Control Sphere vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows a remote attacker to load a document of their choosing into a trusted page via the data attribute of an \u003cobject\u003e element in sanitized HTML. object is the one URI-bearing element in lib/html_sanitize_ex/scrubber/html5.ex never registered through allow_tag_with_uri_attributes/3, and its only guard is a prefix match on lowercase \"javascript:\", so mixed-case variants, data: URIs, protocol-relative URLs and same-origin paths all survive.\n\nThis is not unconditional cross-site scripting. A javascript: URL does not execute through \u003cobject data\u003e in current browsers, data: documents load in an opaque origin, and host-origin script execution additionally requires the application to serve attacker-controlled content from a same-origin path.\n\nThis issue affects html_sanitize_ex: from 0.3.1 before 1.4.5 and from 1.5.0-rc.0 before 1.5.3.","status":"published","published":"2026-08-06T14:48:20.513Z","modified":"2026-10-28T02:31:10.380981641Z","cvss":[{"version":"4.0","score":2.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N","level":"low"}],"cwes":["CWE-829"],"updated_at":"2026-11-02T15:45:14.46177Z"},{"id":"EEF-CVE-2026-66843","title":"html_sanitize_ex HTML5 scrubber keeps attacker-supplied `\u003cobject\u003e` elements, allowing untrusted content embedding","description":"## Summary\n\nInclusion of Functionality from Untrusted Control Sphere vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows a remote attacker to load a document of their choosing into a trusted page via the `data` attribute of an `\u003cobject\u003e` element in sanitized HTML. `object` is the one URI-bearing element in `lib/html_sanitize_ex/scrubber/html5.ex` never registered through `allow_tag_with_uri_attributes/3`, and its only guard is a prefix match on lowercase `\"javascript:\"`, so mixed-case variants, `data:` URIs, protocol-relative URLs and same-origin paths all survive.\n\nThis is not unconditional cross-site scripting. A `javascript:` URL does not execute through `\u003cobject data\u003e` in current browsers, `data:` documents load in an opaque origin, and host-origin script execution additionally requires the application to serve attacker-controlled content from a same-origin path.\n\nThis issue affects html_sanitize_ex: from 0.3.1 before 1.4.5 and from 1.5.0-rc.0 before 1.5.3.\n\n## Workarounds\n\nSanitize with `basic_html/1`, `markdown_html/1` or `strip_tags/1`, none of which allow `object`, or define a custom scrubber that omits it.\n\nA Content-Security-Policy of `object-src 'none'` blocks an injected `\u003cobject\u003e` from loading, and hosting user uploads on a separate origin removes the escalation path.\n\n## Configurations\n\nOnly `HtmlSanitizeEx.html5/1`, and custom scrubbers declared with `use HtmlSanitizeEx, extend: :html5`, allow the `object` element, and the sanitized output must be rendered to other users.\n\nScript execution in the host origin additionally requires the application to serve attacker-controlled HTML from a same-origin path, such as an uploads directory served as `text/html`.","status":"published","published":"2026-08-06T14:48:20.513Z","modified":"2026-09-08T16:15:02.412999777Z","cvss":[{"version":"4.0","score":2.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N","level":"low"}],"cwes":["CWE-829"],"updated_at":"2026-11-02T15:46:33.520522Z"}]}}