{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-118517", "assignerOrgId": "596c5446-0ce5-4ba2-aa66-48b3b757a647", "state": "PUBLISHED", "assignerShortName": "Checkmarx", "dateReserved": "2026-10-28T14:33:36.992Z", "datePublished": "2026-11-05T16:26:52.166Z", "dateUpdated": "2026-11-05T16:52:28.063Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "596c5446-0ce5-4ba2-aa66-48b3b757a647", "shortName": "Checkmarx", "dateUpdated": "2026-11-05T16:26:52.166Z"}, "title": "Symfony: HtmlSanitizer allowLinkHosts() / allowMediaHosts() Bypass via URLs Without a Well-Formed Authority (Incomplete Fix for CVE-2026-45066)", "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-184", "description": "CWE-184 Incomplete List of Disallowed Inputs", "type": "CWE"}]}, {"descriptions": [{"lang": "en", "cweId": "CWE-436", "description": "CWE-436 Interpretation Conflict", "type": "CWE"}]}], "affected": [{"vendor": "sensiolabs", "product": "symfony", "collectionURL": "https://packagist.org/packages/symfony/http-client", "packageName": "symfony/http-client", "repo": "https://github.com/symfony/http-client", "modules": ["Symfony\\Component\\HtmlSanitizer\\TextSanitizer\\UrlSanitizer"], "versions": [{"status": "affected", "version": "6.1.0", "lessThan": "6.4.50", "versionType": "git"}, {"status": "affected", "version": "7.0.0", "lessThan": "7.4.23", "versionType": "git"}, {"status": "affected", "version": "8.0.0", "lessThan": "8.1.11", "versionType": "git"}], "defaultStatus": "unaffected"}], "cpeApplicability": [{"operator": "OR", "nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:sensiolabs:symfony:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.1.0", "versionEndExcluding": "6.4.50"}, {"vulnerable": true, "criteria": "cpe:2.3:a:sensiolabs:symfony:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.0.0", "versionEndExcluding": "7.4.23"}, {"vulnerable": true, "criteria": "cpe:2.3:a:sensiolabs:symfony:*:*:*:*:*:*:*:*", "versionStartIncluding": "8.0.0", "versionEndExcluding": "8.1.11"}]}]}], "descriptions": [{"lang": "en", "value": "The Symfony HtmlSanitizer component UrlSanitizer\u00a0parses URLs differently from browsers, allowing\u00a0the allowLinkHosts() and allowMediaHosts() checks to be bypassed for URLs without a well-formed authority,\u00a0resulting in untrusted hosts being referenced in sanitized output\u00a0in Symfony versions 6.1.x prior to 6.4.50, 7.x prior to 7.4.23, and 8.x prior to 8.1.11.\n\n\n\nUrlSanitizer parses URLs with league/uri, which follows RFC 3986, while browsers follow the WHATWG URL standard.\u00a0For URLs without a well-formed authority, such as http:evil.example, ///evil.example, or https://://evil.example/\u00a0the sanitizer finds no host, whereas browsers resolve them to evil.example. The guard added for CVE-2026-45066 missed the zero-slash form, and the host 0 was also skipped because PHP treats it as falsy.\n\n\n\nThis is exploitable when a host allow-list is combined with allowRelativeLinks(true) or allowRelativeMedias(true). The default configuration is not affected.", "supportingMedia": [{"type": "text/html", "base64": false, "value": "<p>The Symfony HtmlSanitizer component <code>UrlSanitizer</code>&nbsp;parses URLs differently from browsers, allowing&nbsp;<span>the </span><code>allowLinkHosts()</code><span> and </span><code>allowMediaHosts()</code><span> checks to be bypassed for URLs without a well-formed authority,</span><span>&nbsp;</span>resulting in untrusted hosts being referenced in sanitized output<span>&nbsp;in Symfony versions 6.1.x prior to 6.4.50, 7.x prior to 7.4.23, and 8.x prior to 8.1.11.</span></p><p><code>UrlSanitizer</code><span> parses URLs with </span><code>league/uri</code><span>, which follows RFC 3986, while browsers follow the WHATWG URL standard.&nbsp;</span>For URLs without a well-formed authority, such as <code>http:evil.example</code>, <code>///evil.example</code>, or <code>https://://evil.example/&nbsp;</code>t<span>he sanitizer finds no host, whereas browsers resolve them to </span><code>evil.example</code><span>. The guard added for CVE-2026-45066 missed the zero-slash form, and the host </span><code>0</code><span> was also skipped because PHP treats it as falsy.</span></p><p><span>This is exploitable when a host allow-list is combined with </span><code>allowRelativeLinks(true)</code><span> or </span><code>allowRelativeMedias(true)</code><span>. The default configuration is not affected.</span></p>"}]}], "references": [{"url": "https://github.com/symfony/symfony/security/advisories/GHSA-c76g-9c4c-gxrw", "tags": ["third-party-advisory"]}, {"url": "https://github.com/symfony/symfony/commit/f2f47d2eef6c2552c6c5c24953caa94f7901cb43", "tags": ["patch"]}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}], "cvssV4_0": {"attackVector": "NETWORK", "attackComplexity": "LOW", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "userInteraction": "PASSIVE", "vulnConfidentialityImpact": "NONE", "subConfidentialityImpact": "NONE", "vulnIntegrityImpact": "LOW", "subIntegrityImpact": "NONE", "vulnAvailabilityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED", "version": "4.0", "baseSeverity": "LOW", "baseScore": 2.3, "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N"}}], "credits": [{"lang": "en", "value": "Nicolas Grekas", "type": "remediation developer"}, {"lang": "en", "value": "Ilia Alshanetsky", "type": "reporter"}], "source": {"advisory": "GHSA-c76g-9c4c-gxrw", "discovery": "UNKNOWN"}, "x_generator": {"engine": "Vulnogram 1.0.5"}}, "adp": [{"metrics": [{"cvssV3_1": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 4.3, "attackVector": "NETWORK", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N", "integrityImpact": "LOW", "userInteraction": "REQUIRED", "attackComplexity": "LOW", "availabilityImpact": "NONE", "privilegesRequired": "NONE", "confidentialityImpact": "NONE"}}, {"other": {"type": "ssvc", "content": {"timestamp": "2026-11-05T16:49:56.410466Z", "id": "CVE-2026-118517", "options": [{"Exploitation": "poc"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-11-05T16:52:28.063Z"}}]}}

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