{"id":"GHSA-qc95-4862-92fh","summary":"Symfony has an HtmlSanitizer allowLinkHosts() / allowMediaHosts() Bypass via URL-Parser Differentials and \u003carea\u003e Misclassification","details":"### Description\n\n`symfony/html-sanitizer` lets applications sanitise untrusted HTML. The configuration methods `allowLinkHosts([...])` and `allowLinkSchemes([...])` are intended to restrict `\u003ca href\u003e` targets to an allowlist of hosts/schemes; `allowMediaHosts()` / `allowMediaSchemes()` do the same for `\u003cimg src\u003e` etc.\n\nThree distinct bypasses allow a content author to smuggle off-allowlist URLs past these checks. First, `UrlSanitizer::parse()` parses the input following RFC-3986, while browsers follow the WHATWG URL Standard which normalises `\\` to `/` before parsing the authority of \"special\" schemes; so an input like `https://evil\\@trusted.com/` parses with host `trusted.com` server-side but navigates to `https://evil/` in the browser. Second, WHATWG collapses any run of `/` after the scheme into `//`, while RFC-3986 does not; so `https:/evil.com/` and `https:///evil.com/` parse as host-less (skipping the host allowlist) but resolve to `evil.com` in the browser. Third, `UrlAttributeSanitizer` checks `'a' === $element` to route to the link policy and falls through to the media policy otherwise, but `\u003carea\u003e` is a navigable hyperlink equivalent to `\u003ca\u003e`; so `\u003carea href\u003e` was sanitised against the media policy (which typically allows `data:` and may have no host allowlist), bypassing `allowLinkHosts()` / `allowLinkSchemes()` entirely.\n\n### Resolution\n\n`UrlSanitizer::sanitize()` now rejects URLs that contain a backslash or that use a special scheme (`http`, `https`, `ftp`, `ws`, `wss`) followed by a single slash or three slashes before parsing, eliminating the parser-differential bypasses. `UrlAttributeSanitizer` now applies the link policy to both `\u003ca\u003e` and `\u003carea\u003e` elements.\n\nThe patch for this issue is available [here](https://github.com/symfony/symfony/commit/d506b556d3d3906f3e8660ad82257ce87edbaac4) for branch 5.4.\n\n### Credits\n\nSymfony would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and providing the fix.","aliases":["CVE-2026-45066"],"modified":"2026-09-10T03:50:47.394247065Z","published":"2026-05-27T20:13:04Z","database_specific":{"cwe_ids":["CWE-184","CWE-436"],"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2026-05-27T20:13:04Z","nvd_published_at":null},"references":[{"type":"WEB","url":"https://github.com/symfony/symfony/security/advisories/GHSA-qc95-4862-92fh"},{"type":"WEB","url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/html-sanitizer/CVE-2026-45066.yaml"},{"type":"WEB","url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2026-45066.yaml"},{"type":"PACKAGE","url":"https://github.com/symfony/symfony"},{"type":"WEB","url":"https://symfony.com/cve-2026-45066"}],"affected":[{"package":{"name":"symfony/html-sanitizer","ecosystem":"Packagist","purl":"pkg:composer/symfony/html-sanitizer"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.1.0"},{"fixed":"6.4.40"}]}],"versions":["v6.1.0","v6.1.11","v6.1.9","v6.2.0","v6.2.0-BETA1","v6.2.0-RC1","v6.2.2","v6.2.5","v6.2.7","v6.3.0","v6.3.0-BETA1","v6.3.0-RC1","v6.3.12","v6.3.4","v6.3.7","v6.4.0","v6.4.0-BETA1","v6.4.0-BETA2","v6.4.0-RC1","v6.4.12","v6.4.13","v6.4.17","v6.4.18","v6.4.21","v6.4.24","v6.4.25","v6.4.28","v6.4.3","v6.4.35","v6.4.4","v6.4.7","v6.4.8"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-qc95-4862-92fh/GHSA-qc95-4862-92fh.json"}},{"package":{"name":"symfony/html-sanitizer","ecosystem":"Packagist","purl":"pkg:composer/symfony/html-sanitizer"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"7.0.0"},{"fixed":"7.4.12"}]}],"versions":["v7.0.0","v7.0.3","v7.0.4","v7.0.7","v7.0.8","v7.1.0","v7.1.0-BETA1","v7.1.0-RC1","v7.1.1","v7.1.10","v7.1.11","v7.1.5","v7.1.6","v7.2.0","v7.2.0-BETA1","v7.2.0-RC1","v7.2.2","v7.2.3","v7.2.6","v7.2.9","v7.3.0","v7.3.0-BETA1","v7.3.0-RC1","v7.3.2","v7.3.3","v7.3.6","v7.4.0","v7.4.0-BETA1","v7.4.0-BETA2","v7.4.0-RC1","v7.4.7","v7.4.8"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-qc95-4862-92fh/GHSA-qc95-4862-92fh.json"}},{"package":{"name":"symfony/html-sanitizer","ecosystem":"Packagist","purl":"pkg:composer/symfony/html-sanitizer"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"8.0.0"},{"fixed":"8.0.12"}]}],"versions":["v8.0.0","v8.0.7","v8.0.8"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-qc95-4862-92fh/GHSA-qc95-4862-92fh.json"}},{"package":{"name":"symfony/symfony","ecosystem":"Packagist","purl":"pkg:composer/symfony/symfony"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.1.0"},{"fixed":"6.4.40"}]}],"versions":["v6.1.0","v6.1.1","v6.1.10","v6.1.11","v6.1.12","v6.1.2","v6.1.3","v6.1.4","v6.1.5","v6.1.6","v6.1.7","v6.1.8","v6.1.9","v6.2.0","v6.2.0-BETA1","v6.2.0-BETA2","v6.2.0-BETA3","v6.2.0-RC1","v6.2.0-RC2","v6.2.1","v6.2.10","v6.2.11","v6.2.12","v6.2.13","v6.2.14","v6.2.2","v6.2.3","v6.2.4","v6.2.5","v6.2.6","v6.2.7","v6.2.8","v6.2.9","v6.3.0","v6.3.0-BETA1","v6.3.0-BETA2","v6.3.0-BETA3","v6.3.0-RC1","v6.3.0-RC2","v6.3.1","v6.3.10","v6.3.11","v6.3.12","v6.3.2","v6.3.3","v6.3.4","v6.3.5","v6.3.6","v6.3.7","v6.3.8","v6.3.9","v6.4.0","v6.4.0-BETA1","v6.4.0-BETA2","v6.4.0-BETA3","v6.4.0-RC1","v6.4.0-RC2","v6.4.1","v6.4.10","v6.4.11","v6.4.12","v6.4.13","v6.4.14","v6.4.15","v6.4.16","v6.4.17","v6.4.18","v6.4.19","v6.4.2","v6.4.20","v6.4.21","v6.4.22","v6.4.23","v6.4.24","v6.4.25","v6.4.26","v6.4.27","v6.4.28","v6.4.29","v6.4.3","v6.4.30","v6.4.31","v6.4.32","v6.4.33","v6.4.34","v6.4.35","v6.4.36","v6.4.37","v6.4.38","v6.4.39","v6.4.4","v6.4.5","v6.4.6","v6.4.7","v6.4.8","v6.4.9"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-qc95-4862-92fh/GHSA-qc95-4862-92fh.json"}},{"package":{"name":"symfony/symfony","ecosystem":"Packagist","purl":"pkg:composer/symfony/symfony"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"7.0.0"},{"fixed":"7.4.12"}]}],"versions":["v7.0.0","v7.0.1","v7.0.10","v7.0.2","v7.0.3","v7.0.4","v7.0.5","v7.0.6","v7.0.7","v7.0.8","v7.0.9","v7.1.0","v7.1.0-BETA1","v7.1.0-RC1","v7.1.1","v7.1.10","v7.1.11","v7.1.2","v7.1.3","v7.1.4","v7.1.5","v7.1.6","v7.1.7","v7.1.8","v7.1.9","v7.2.0","v7.2.0-BETA1","v7.2.0-BETA2","v7.2.0-RC1","v7.2.1","v7.2.2","v7.2.3","v7.2.4","v7.2.5","v7.2.6","v7.2.7","v7.2.8","v7.2.9","v7.3.0","v7.3.0-BETA1","v7.3.0-BETA2","v7.3.0-RC1","v7.3.1","v7.3.10","v7.3.11","v7.3.2","v7.3.3","v7.3.4","v7.3.5","v7.3.6","v7.3.7","v7.3.8","v7.3.9","v7.4.0","v7.4.0-BETA1","v7.4.0-BETA2","v7.4.0-RC1","v7.4.0-RC2","v7.4.0-RC3","v7.4.1","v7.4.10","v7.4.11","v7.4.2","v7.4.3","v7.4.4","v7.4.5","v7.4.6","v7.4.7","v7.4.8","v7.4.9"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-qc95-486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