{"id":"EEF-CVE-2026-66829","summary":"html_sanitize_ex HTML5 scrubber keeps attacker-supplied meta refresh, allowing forced cross-origin redirection","details":"## Summary\n\nURL Redirection to Untrusted Site ('Open Redirect') vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows a remote attacker to force visitors of a page to navigate to a site of the attacker's choosing via a `\u003cmeta http-equiv=\"refresh\"\u003e` element in sanitized HTML. `HtmlSanitizeEx.html5/1` keeps attacker-supplied `\u003cmeta\u003e` elements in its output. A `meta` element acts on the whole document rather than on the fragment it was embedded in, so it can also declare document-wide directives such as `Content-Security-Policy`.\n\nThis is not cross-site scripting. Browsers do not navigate a meta refresh to a `javascript:` URL, so the uppercase `JAVASCRIPT:` filter bypass yields no script execution and none was demonstrated.\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 `meta`, or define a custom scrubber that omits it.\n\n## Configurations\n\nOnly `HtmlSanitizeEx.html5/1`, and custom scrubbers declared with `use HtmlSanitizeEx, extend: :html5`, allow the `meta` element, and the sanitized output must be rendered to other users.","aliases":["CVE-2026-66829","GHSA-2c6f-3j54-xpcr"],"modified":"2026-09-08T16:15:02.418063995Z","published":"2026-08-06T14:49:23.468Z","database_specific":{"cwe_ids":["CWE-601"],"capec_ids":["CAPEC-154"],"cpe_ids":["cpe:2.3:a:rrrene:html_sanitize_ex:*:*:*:*:*:*:*:*"]},"references":[{"type":"ADVISORY","url":"https://github.com/rrrene/html_sanitize_ex/security/advisories/GHSA-2c6f-3j54-xpcr"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-66829.html"},{"type":"FIX","url":"https://github.com/rrrene/html_sanitize_ex/commit/9f7e38be51edc38f132dfe994f37af5cf5e0e76f"},{"type":"FIX","url":"https://github.com/rrrene/html_sanitize_ex/commit/29454dc99513fd9b5b6429ab7b6695ad09889227"},{"type":"PACKAGE","url":"https://hex.pm/packages/html_sanitize_ex"}],"affected":[{"package":{"name":"html_sanitize_ex","ecosystem":"Hex","purl":"pkg:hex/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"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-66829.json"}},{"ranges":[{"type":"GIT","repo":"https://github.com/rrrene/html_sanitize_ex","events":[{"introduced":"8976d64ea0b77d26093a94a43ec48a3978e8d028"},{"fixed":"9f7e38be51edc38f132dfe994f37af5cf5e0e76f"},{"fixed":"29454dc99513fd9b5b6429ab7b6695ad09889227"}]}],"versions":["v1.4.4","v1.5.2","v1.5.1","v1.5.0","v1.5.0-rc.0","v1.4.3","v1.4.2","v1.4.1","v1.2.0","v1.0.1","v1.0.0","v0.3.1"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-66829.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N"}],"credits":[{"name":"Peter Ullrich","type":"FINDER"},{"name":"Jonatan Männchen / EEF","type":"ANALYST"},{"name":"René Föhring","type":"REMEDIATION_DEVELOPER"}]}