{"id":"CVE-2026-66829","state":"PUBLISHED","title":"html_sanitize_ex HTML5 scrubber keeps attacker-supplied meta refresh, allowing forced cross-origin redirection","description":"URL 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 element in sanitized HTML. HtmlSanitizeEx.html5/1 keeps attacker-supplied 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.","publishedAt":"2026-08-06T14:49:23.468Z","updatedAt":"2026-08-19T11:50:39.885Z","severity":{"score":2.3,"label":"Low","version":"4.0","vector":"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","source":"EEF"},"assigner":"EEF","products":["rrrene html_sanitize_ex"],"affected":[{"vendor":"rrrene","product":"html_sanitize_ex","packageName":"html_sanitize_ex","packageURL":"pkg:hex/html_sanitize_ex","defaultStatus":"unaffected","versions":[{"version":"0.3.1","status":"affected","lessThan":"1.4.5","versionType":"semver"},{"version":"1.5.0-rc.0","status":"affected","lessThan":"1.5.3","versionType":"semver"}],"collectionURL":"https://repo.hex.pm","cpes":["cpe:2.3:a:rrrene:html_sanitize_ex:*:*:*:*:*:*:*:*"],"modules":["Elixir.HtmlSanitizeEx.Scrubber.HTML5","Elixir.HtmlSanitizeEx"],"programFiles":["lib/html_sanitize_ex/scrubber/html5.ex","lib/html_sanitize_ex.ex"],"programRoutines":[{"name":"'Elixir.HtmlSanitizeEx.Scrubber.HTML5':scrub_attribute/2"},{"name":"'Elixir.HtmlSanitizeEx.Scrubber.HTML5':sanitize/1"},{"name":"'Elixir.HtmlSanitizeEx':html5/1"}],"repo":"https://github.com/rrrene/html_sanitize_ex"},{"vendor":"rrrene","product":"html_sanitize_ex","packageName":"rrrene/html_sanitize_ex","packageURL":"pkg:github/rrrene/html_sanitize_ex","defaultStatus":"unaffected","versions":[{"version":"8976d64ea0b77d26093a94a43ec48a3978e8d028","status":"affected","lessThan":"*","changes":[{"at":"9f7e38be51edc38f132dfe994f37af5cf5e0e76f","status":"unaffected"},{"at":"29454dc99513fd9b5b6429ab7b6695ad09889227","status":"unaffected"}],"versionType":"git"}],"collectionURL":"https://github.com","cpes":["cpe:2.3:a:rrrene:html_sanitize_ex:*:*:*:*:*:*:*:*"],"modules":["Elixir.HtmlSanitizeEx.Scrubber.HTML5","Elixir.HtmlSanitizeEx"],"programFiles":["lib/html_sanitize_ex/scrubber/html5.ex","lib/html_sanitize_ex.ex"],"programRoutines":[{"name":"'Elixir.HtmlSanitizeEx.Scrubber.HTML5':scrub_attribute/2"},{"name":"'Elixir.HtmlSanitizeEx.Scrubber.HTML5':sanitize/1"},{"name":"'Elixir.HtmlSanitizeEx':html5/1"}],"repo":"https://github.com/rrrene/html_sanitize_ex"}],"references":["https://github.com/rrrene/html_sanitize_ex/security/advisories/GHSA-2c6f-3j54-xpcr","https://cna.erlef.org/cves/CVE-2026-66829.html","https://osv.dev/vulnerability/EEF-CVE-2026-66829","https://github.com/rrrene/html_sanitize_ex/commit/9f7e38be51edc38f132dfe994f37af5cf5e0e76f","https://github.com/rrrene/html_sanitize_ex/commit/29454dc99513fd9b5b6429ab7b6695ad09889227"],"weaknesses":["CWE-601"],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/66xxx/CVE-2026-66829.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-66829","state":"PUBLISHED","datePublished":"2026-08-06T14:49:23.468Z","dateUpdated":"2026-08-19T11:50:39.885Z","assignerShortName":"EEF","assignerOrgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","dateReserved":"2026-08-06T08:15:02.719Z"},"containers":{"cna":{"title":"html_sanitize_ex HTML5 scrubber keeps attacker-supplied meta refresh, allowing forced cross-origin redirection","descriptions":[{"lang":"en","value":"URL 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 element in sanitized HTML. HtmlSanitizeEx.html5/1 keeps attacker-supplied 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."}],"affected":[{"vendor":"rrrene","product":"html_sanitize_ex","packageName":"html_sanitize_ex","packageURL":"pkg:hex/html_sanitize_ex","defaultStatus":"unaffected","versions":[{"version":"0.3.1","status":"affected","lessThan":"1.4.5","versionType":"semver"},{"version":"1.5.0-rc.0","status":"affected","lessThan":"1.5.3","versionType":"semver"}],"collectionURL":"https://repo.hex.pm","cpes":["cpe:2.3:a:rrrene:html_sanitize_ex:*:*:*:*:*:*:*:*"],"modules":["Elixir.HtmlSanitizeEx.Scrubber.HTML5","Elixir.HtmlSanitizeEx"],"programFiles":["lib/html_sanitize_ex/scrubber/html5.ex","lib/html_sanitize_ex.ex"],"programRoutines":[{"name":"'Elixir.HtmlSanitizeEx.Scrubber.HTML5':scrub_attribute/2"},{"name":"'Elixir.HtmlSanitizeEx.Scrubber.HTML5':sanitize/1"},{"name":"'Elixir.HtmlSanitizeEx':html5/1"}],"repo":"https://github.com/rrrene/html_sanitize_ex"},{"vendor":"rrrene","product":"html_sanitize_ex","packageName":"rrrene/html_sanitize_ex","packageURL":"pkg:github/rrrene/html_sanitize_ex","defaultStatus":"unaffected","versions":[{"version":"8976d64ea0b77d26093a94a43ec48a3978e8d028","status":"affected","lessThan":"*","changes":[{"at":"9f7e38be51edc38f132dfe994f37af5cf5e0e76f","status":"unaffected"},{"at":"29454dc99513fd9b5b6429ab7b6695ad09889227","status":"unaffected"}],"versionType":"git"}],"collectionURL":"https://github.com","cpes":["cpe:2.3:a:rrrene:html_sanitize_ex:*:*:*:*:*:*:*:*"],"modules":["Elixir.HtmlSanitizeEx.Scrubber.HTML5","Elixir.HtmlSanitizeEx"],"programFiles":["lib/html_sanitize_ex/scrubber/html5.ex","lib/html_sanitize_ex.ex"],"programRoutines":[{"name":"'Elixir.HtmlSanitizeEx.Scrubber.HTML5':scrub_attribute/2"},{"name":"'Elixir.HtmlSanitizeEx.Scrubber.HTML5':sanitize/1"},{"name":"'Elixir.HtmlSanitizeEx':html5/1"}],"repo":"https://github.com/rrrene/html_sanitize_ex"}],"references":[{"url":"https://github.com/rrrene/html_sanitize_ex/security/advisories/GHSA-2c6f-3j54-xpcr","tags":["vendor-advisory","related"]},{"url":"https://cna.erlef.org/cves/CVE-2026-66829.html","tags":["related"]},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-66829","tags":["related"]},{"url":"https://github.com/rrrene/html_sanitize_ex/commit/9f7e38be51edc38f132dfe994f37af5cf5e0e76f","tags":["patch"]},{"url":"https://github.com/rrrene/html_sanitize_ex/commit/29454dc99513fd9b5b6429ab7b6695ad09889227","tags":["patch"]}],"metrics":[{"cvssV4_0":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"PRESENT","attackVector":"NETWORK","baseScore":2.3,"baseSeverity":"LOW","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"LOW","userInteraction":"PASSIVE","valueDensity":"NOT_DEFINED","vectorString":"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","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnerabilityResponseEffort":"NOT_DEFINED"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-601","description":"CWE-601 URL Redirection to Untrusted Site ('Open Redirect')","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"EEF","orgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","dateUpdated":"2026-08-19T11:50:39.885Z"},"configurations":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"

Only 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.

"},{"base64":false,"type":"text/markdown","value":"Only `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."}],"value":"Only 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."}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:a:rrrene:html_sanitize_ex:*:*:*:*:*:*:*:*","versionEndExcluding":"1.4.5","versionStartIncluding":"0.3.1","vulnerable":true},{"criteria":"cpe:2.3:a:rrrene:html_sanitize_ex:*:*:*:*:*:*:*:*","versionEndExcluding":"1.5.3","versionStartIncluding":"1.5.0-rc.0","vulnerable":true}],"negate":false,"operator":"OR"}],"operator":"AND"}],"credits":[{"lang":"en","type":"finder","value":"Peter Ullrich"},{"lang":"en","type":"analyst","value":"Jonatan Männchen / EEF"},{"lang":"en","type":"remediation developer","value":"René Föhring"}],"impacts":[{"capecId":"CAPEC-154","descriptions":[{"lang":"en","value":"CAPEC-154 Resource Location Spoofing"}]}],"source":{"discovery":"EXTERNAL"},"workarounds":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"

Sanitize with basic_html/1, markdown_html/1 or strip_tags/1, none of which allow meta, or define a custom scrubber that omits it.

"},{"base64":false,"type":"text/markdown","value":"Sanitize with `basic_html/1`, `markdown_html/1` or `strip_tags/1`, none of which allow `meta`, or define a custom scrubber that omits it."}],"value":"Sanitize with basic_html/1, markdown_html/1 or strip_tags/1, none of which allow meta, or define a custom scrubber that omits it."}]},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-06T15:42:40.366099Z","id":"CVE-2026-66829","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-06T15:42:46.200Z"}}]}}}