CVE-2026-123339

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When <code>framework.trusted_hosts</code> is configured, a forwarded host outside the list is rejected, but the scheme and port can still be changed.</div>"}]}], "references": [{"url": "https://github.com/symfony/symfony/security/advisories/GHSA-wg5q-m2ww-f3c9", "tags": ["third-party-advisory"]}, {"url": "https://github.com/symfony/symfony/commit/4b4e683b2c280083c6758bb776af952076add612", "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": "LOW", "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:L/SI:N/SA:N"}}], "credits": [{"lang": "en", "value": "Nicolas Grekas", "type": "reporter"}], "source": {"advisory": "GHSA-wg5q-m2ww-f3c9", "discovery": "UNKNOWN"}, "x_generator": {"engine": "Vulnogram 1.0.5"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-11-06T14:53:34.938730Z", "id": "CVE-2026-123339", "options": [{"Exploitation": "none"}, {"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": "2026-11-06T15:21:40.439Z"}}]}}

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With the default configuration (framework.trusted_proxies unset), all forwarded headers, including X-Forwarded-Host, are trusted during that window. Applications served through php-fpm, mod_php, or a proxy on another host are not affected. When framework.trusted_hosts is configured, a forwarded host outside the list is rejected, but the scheme and port can still be changed.", "supportingMedia": [{"type": "text/html", "value": "Improper trust of forwarded headers in&nbsp;<code>RouterListener::onKernelFinishRequest()</code>&nbsp;in Symfony HttpKernel versions prior to 5.4.56, 6.x prior to 6.4.50, 7.x prior to 7.4.23, and 8.x prior to 8.1.11 allows a remote attacker to control the host, scheme, and port of absolute URLs generated for the rest of the request, poisoning links in pages stored by a shared cache and in e-mails sent after the page was rendered.<div>When a page renders an inline fragment (<code>render()</code> in Twig, or an ESI tag rendered inline), <code>SubRequestHandler</code> temporarily adds <code>127.0.0.1</code> to the trusted proxies, and <code>RouterListener</code> rebuilds the router context from the main request while that trust is still active, so the <code>X-Forwarded-*</code> and <code>Forwarded</code> headers of a request whose client address is <code>127.0.0.1</code> are trusted even though that address is not a configured trusted proxy.&nbsp;<span>From that point on, every absolute URL the router generates for the rest of the main request takes its host, scheme, and port from headers sent by the client, including URLs produced by </span><code>url()</code><span> in Twig and by </span><code>UrlGeneratorInterface::ABSOLUTE_URL</code><span>.</span></div><div>Applications are affected when they are reached over HTTP from <code>127.0.0.1</code>, for example behind a TLS terminator, reverse proxy, local HTTP cache, or sidecar proxy on the same host, and that proxy passes the client\u2019s forwarded headers along. With the default configuration (<code>framework.trusted_proxies</code> unset), all forwarded headers, including <code>X-Forwarded-Host</code>, are trusted during that window. Applications served through php-fpm, mod_php, or a proxy on another host are not affected. When <code>framework.trusted_hosts</code> is configured, a forwarded host outside the list is rejected, but the scheme and port can still be changed.</div>", "base64": false}]}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-348", "description": "CWE-348 Use of Less Trusted Source"}]}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:sensiolabs:symfony:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.4.56", "versionStartIncluding": "0"}, {"criteria": "cpe:2.3:a:sensiolabs:symfony:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.4.50", "versionStartIncluding": "6.0.0"}, {"criteria": "cpe:2.3:a:sensiolabs:symfony:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "7.4.23", "versionStartIncluding": "7.0.0"}, {"criteria": "cpe:2.3:a:sensiolabs:symfony:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "8.1.11", "versionStartIncluding": "8.0.0"}], "operator": "OR"}], "operator": "OR"}], "providerMetadata": {"orgId": "596c5446-0ce5-4ba2-aa66-48b3b757a647", "shortName": "Checkmarx", "dateUpdated": "2026-11-06T14:40:34.836Z"}}}, "cveMetadata": {"cveId": "CVE-2026-123339", "state": "PUBLISHED", "dateUpdated": "2026-11-06T15:21:40.439Z", "dateReserved": "2026-11-05T18:43:28.175Z", "assignerOrgId": "596c5446-0ce5-4ba2-aa66-48b3b757a647", "datePublished": "2026-11-06T14:40:34.836Z", "assignerShortName": "Checkmarx"}, "dataVersion": "5.2"}

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With the default configuration (framework.trusted_proxies unset), all forwarded headers, including X-Forwarded-Host, are trusted during that window. Applications served through php-fpm, mod_php, or a proxy on another host are not affected. 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