{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-66370", "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "state": "PUBLISHED", "assignerShortName": "EEF", "dateReserved": "2026-08-06T10:15:01.808Z", "datePublished": "2026-08-06T14:49:15.841Z", "dateUpdated": "2026-08-06T14:49:15.841Z"}, "containers": {"cna": {"affected": [{"collectionURL": "https://repo.hex.pm", "cpes": ["cpe:2.3:a:rrrene:html_sanitize_ex:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["Elixir.HtmlSanitizeEx.Scrubber.HTML5", "Elixir.HtmlSanitizeEx"], "packageName": "html_sanitize_ex", "packageURL": "pkg:hex/html_sanitize_ex", "product": "html_sanitize_ex", "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", "versions": [{"lessThan": "1.5.3", "status": "affected", "version": "0.3.1", "versionType": "semver"}]}, {"collectionURL": "https://github.com", "cpes": ["cpe:2.3:a:rrrene:html_sanitize_ex:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["Elixir.HtmlSanitizeEx.Scrubber.HTML5", "Elixir.HtmlSanitizeEx"], "packageName": "rrrene/html_sanitize_ex", "packageURL": "pkg:github/rrrene/html_sanitize_ex", "product": "html_sanitize_ex", "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", "versions": [{"lessThan": "a1e804ed997e780ea71d14393cf2f701330553a6", "status": "affected", "version": "8976d64ea0b77d26093a94a43ec48a3978e8d028", "versionType": "git"}]}], "configurations": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>Only <code>HtmlSanitizeEx.html5/1</code>, and custom scrubbers declared with <code>use HtmlSanitizeEx, extend: :html5</code>, allow the <code>input</code> element, and the sanitized output must be rendered to other users.</p>\n<p>The rendering page must also contain a form with an <code>id</code>, since that <code>id</code> is what the injected <code>form</code> attribute binds to.</p>"}, {"base64": false, "type": "text/markdown", "value": "Only `HtmlSanitizeEx.html5/1`, and custom scrubbers declared with `use HtmlSanitizeEx, extend: :html5`, allow the `input` element, and the sanitized output must be rendered to other users.\n\nThe rendering page must also contain a form with an `id`, since that `id` is what the injected `form` attribute binds to."}], "value": "Only HtmlSanitizeEx.html5/1, and custom scrubbers declared with use HtmlSanitizeEx, extend: :html5, allow the input element, and the sanitized output must be rendered to other users.\n\nThe rendering page must also contain a form with an id, since that id is what the injected form attribute binds to."}], "cpeApplicability": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:rrrene:html_sanitize_ex:*:*:*:*:*:*:*:*", "versionEndExcluding": "1.5.3", "versionStartIncluding": "0.3.1", "vulnerable": true}], "negate": false, "operator": "OR"}], "operator": "AND"}], "credits": [{"lang": "en", "type": "finder", "value": "Peter Ullrich"}, {"lang": "en", "type": "analyst", "value": "Jonatan M\u00e4nnchen / EEF"}, {"lang": "en", "type": "remediation developer", "value": "Ren\u00e9 F\u00f6hring"}], "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>URL Redirection to Untrusted Site ('Open Redirect') vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows an unauthenticated remote attacker to retarget a form already on the rendering page and receive whatever the victim submits, including credentials, via the <code>form</code> and <code>formaction</code> attributes on an <code>&lt;input&gt;</code> element in sanitized HTML. HTML's <code>form</code> attribute associates an input with any form on the page by its <code>id</code> even when the input sits outside that form, and <code>formaction</code> on a submit control overrides the owning form's <code>action</code>. Neither attribute receives a scheme check, so an absolute cross-origin URL survives sanitizing.</p>\n<p>No script executes. The scrubber allows neither <code>form</code> nor <code>button</code>, so the attacker cannot introduce a form of their own and the rendering page must already contain a form carrying an <code>id</code>.</p>\n<p>This issue affects html_sanitize_ex: from 0.3.1 before 1.5.3.</p>"}, {"base64": false, "type": "text/markdown", "value": "URL Redirection to Untrusted Site ('Open Redirect') vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows an unauthenticated remote attacker to retarget a form already on the rendering page and receive whatever the victim submits, including credentials, via the `form` and `formaction` attributes on an `<input>` element in sanitized HTML. HTML's `form` attribute associates an input with any form on the page by its `id` even when the input sits outside that form, and `formaction` on a submit control overrides the owning form's `action`. Neither attribute receives a scheme check, so an absolute cross-origin URL survives sanitizing.\n\nNo script executes. The scrubber allows neither `form` nor `button`, so the attacker cannot introduce a form of their own and the rendering page must already contain a form carrying an `id`.\n\nThis issue affects html_sanitize_ex: from 0.3.1 before 1.5.3."}], "value": "URL Redirection to Untrusted Site ('Open Redirect') vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows an unauthenticated remote attacker to retarget a form already on the rendering page and receive whatever the victim submits, including credentials, via the form and formaction attributes on an <input> element in sanitized HTML. HTML's form attribute associates an input with any form on the page by its id even when the input sits outside that form, and formaction on a submit control overrides the owning form's action. Neither attribute receives a scheme check, so an absolute cross-origin URL survives sanitizing.\n\nNo script executes. The scrubber allows neither form nor button, so the attacker cannot introduce a form of their own and the rendering page must already contain a form carrying an id.\n\nThis issue affects html_sanitize_ex: from 0.3.1 before 1.5.3."}], "impacts": [{"capecId": "CAPEC-154", "descriptions": [{"lang": "en", "value": "CAPEC-154 Resource Location Spoofing"}]}], "metrics": [{"cvssV4_0": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "attackVector": "NETWORK", "baseScore": 4.8, "baseSeverity": "MEDIUM", "privilegesRequired": "NONE", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "HIGH", "subIntegrityImpact": "LOW", "userInteraction": "ACTIVE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:N/SC:H/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": {"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "shortName": "EEF", "dateUpdated": "2026-08-06T14:49:15.841Z"}, "references": [{"tags": ["vendor-advisory", "related"], "url": "https://github.com/rrrene/html_sanitize_ex/security/advisories/GHSA-w3f9-jjhw-wwvq"}, {"tags": ["related"], "url": "https://cna.erlef.org/cves/CVE-2026-66370.html"}, {"tags": ["related"], "url": "https://osv.dev/vulnerability/EEF-CVE-2026-66370"}, {"tags": ["patch"], "url": "https://github.com/rrrene/html_sanitize_ex/commit/a1e804ed997e780ea71d14393cf2f701330553a6"}], "source": {"discovery": "EXTERNAL"}, "title": "html_sanitize_ex HTML5 scrubber keeps attacker-supplied form-association attributes, allowing form hijacking", "workarounds": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>Sanitize with <code>basic_html/1</code>, <code>markdown_html/1</code> or <code>strip_tags/1</code>, none of which allow <code>input</code>, or define a custom scrubber that omits it.</p>\n<p>Omitting the <code>id</code> attribute from the page's own forms, or giving them values an attacker cannot predict, removes the anchor the injected <code>form</code> attribute needs.</p>"}, {"base64": false, "type": "text/markdown", "value": "Sanitize with `basic_html/1`, `markdown_html/1` or `strip_tags/1`, none of which allow `input`, or define a custom scrubber that omits it.\n\nOmitting the `id` attribute from the page's own forms, or giving them values an attacker cannot predict, removes the anchor the injected `form` attribute needs."}], "value": "Sanitize with basic_html/1, markdown_html/1 or strip_tags/1, none of which allow input, or define a custom scrubber that omits it.\n\nOmitting the id attribute from the page's own forms, or giving them values an attacker cannot predict, removes the anchor the injected form attribute needs."}]}}}

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