CVE-2026-123339 (GCVE-0-2026-123339)
Vulnerability from cvelistv5 – Published: 2026-11-06 14:40 – Updated: 2026-11-06 15:21
VLAI
EPSS
VEX
Title
Symfony: Inline Fragments Let Untrusted Forwarded Headers Set the Host, Scheme and Port of the URLs Generated for the Main Request
Summary
Improper trust of forwarded headers in RouterListener::onKernelFinishRequest() 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.When a page renders an inline fragment (render() in Twig, or an ESI tag rendered inline), SubRequestHandler temporarily adds 127.0.0.1 to the trusted proxies, and RouterListener rebuilds the router context from the main request while that trust is still active, so the X-Forwarded-* and Forwarded headers of a request whose client address is 127.0.0.1 are trusted even though that address is not a configured trusted proxy. 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 url() in Twig and by UrlGeneratorInterface::ABSOLUTE_URL.
Applications are affected when they are reached over HTTP from 127.0.0.1, for example behind a TLS terminator, reverse proxy, local HTTP cache, or sidecar proxy on the same host, and that proxy passes the client’s forwarded headers along. 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.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-11-06 14:53 UTC
CWE
- CWE-348 - Use of Less Trusted Source
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://github.com/symfony/symfony/security/advis… | third-party-advisory |
| https://github.com/symfony/symfony/commit/4b4e683… | patch |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| sensiolabs | symfony |
Affected:
0 , < 5.4.56
(git)
Affected: 6.0.0 , < 6.4.50 (git) Affected: 7.0.0 , < 7.4.23 (git) Affected: 8.0.0 , < 8.1.11 (git) cpe:2.3:a:sensiolabs:symfony:*:*:*:*:*:*:*:* cpe:2.3:a:sensiolabs:symfony:*:*:*:*:*:*:*:* cpe:2.3:a:sensiolabs:symfony:*:*:*:*:*:*:*:* cpe:2.3:a:sensiolabs:symfony:*:*:*:*:*:*:*:* |
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"value": "Improper trust of forwarded headers in\u0026nbsp;\u003ccode\u003eRouterListener::onKernelFinishRequest()\u003c/code\u003e\u0026nbsp;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.\u003cdiv\u003eWhen a page renders an inline fragment (\u003ccode\u003erender()\u003c/code\u003e in Twig, or an ESI tag rendered inline), \u003ccode\u003eSubRequestHandler\u003c/code\u003e temporarily adds \u003ccode\u003e127.0.0.1\u003c/code\u003e to the trusted proxies, and \u003ccode\u003eRouterListener\u003c/code\u003e rebuilds the router context from the main request while that trust is still active, so the \u003ccode\u003eX-Forwarded-*\u003c/code\u003e and \u003ccode\u003eForwarded\u003c/code\u003e headers of a request whose client address is \u003ccode\u003e127.0.0.1\u003c/code\u003e are trusted even though that address is not a configured trusted proxy.\u0026nbsp;\u003cspan\u003eFrom 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 \u003c/span\u003e\u003ccode\u003eurl()\u003c/code\u003e\u003cspan\u003e in Twig and by \u003c/span\u003e\u003ccode\u003eUrlGeneratorInterface::ABSOLUTE_URL\u003c/code\u003e\u003cspan\u003e.\u003c/span\u003e\u003c/div\u003e\u003cdiv\u003eApplications are affected when they are reached over HTTP from \u003ccode\u003e127.0.0.1\u003c/code\u003e, 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 (\u003ccode\u003eframework.trusted_proxies\u003c/code\u003e unset), all forwarded headers, including \u003ccode\u003eX-Forwarded-Host\u003c/code\u003e, are trusted during that window. Applications served through php-fpm, mod_php, or a proxy on another host are not affected. When \u003ccode\u003eframework.trusted_hosts\u003c/code\u003e is configured, a forwarded host outside the list is rejected, but the scheme and port can still be changed.\u003c/div\u003e"
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],
"value": "Improper trust of forwarded headers in\u00a0RouterListener::onKernelFinishRequest()\u00a0in 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.When a page renders an inline fragment (render() in Twig, or an ESI tag rendered inline), SubRequestHandler temporarily adds 127.0.0.1 to the trusted proxies, and RouterListener rebuilds the router context from the main request while that trust is still active, so the X-Forwarded-* and Forwarded headers of a request whose client address is 127.0.0.1 are trusted even though that address is not a configured trusted proxy.\u00a0From 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 url() in Twig and by UrlGeneratorInterface::ABSOLUTE_URL.\n\nApplications are affected when they are reached over HTTP from 127.0.0.1, 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 (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."
}
],
"metrics": [
{
"cvssV4_0": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "NETWORK",
"baseScore": 2.3,
"baseSeverity": "LOW",
"exploitMaturity": "NOT_DEFINED",
"privilegesRequired": "NONE",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "LOW",
"subIntegrityImpact": "NONE",
"userInteraction": "PASSIVE",
"valueDensity": "NOT_DEFINED",
"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",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "LOW",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"format": "CVSS",
"scenarios": [
{
"lang": "en",
"value": "GENERAL"
}
]
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-348",
"description": "CWE-348 Use of Less Trusted Source",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-11-06T14:40:34.836Z",
"orgId": "596c5446-0ce5-4ba2-aa66-48b3b757a647",
"shortName": "Checkmarx"
},
"references": [
{
"tags": [
"third-party-advisory"
],
"url": "https://github.com/symfony/symfony/security/advisories/GHSA-wg5q-m2ww-f3c9"
},
{
"tags": [
"patch"
],
"url": "https://github.com/symfony/symfony/commit/4b4e683b2c280083c6758bb776af952076add612"
}
],
"source": {
"advisory": "GHSA-wg5q-m2ww-f3c9",
"discovery": "UNKNOWN"
},
"title": "Symfony: Inline Fragments Let Untrusted Forwarded Headers Set the Host, Scheme and Port of the URLs Generated for the Main Request",
"x_generator": {
"engine": "Vulnogram 1.0.5"
}
}
},
"cveMetadata": {
"assignerOrgId": "596c5446-0ce5-4ba2-aa66-48b3b757a647",
"assignerShortName": "Checkmarx",
"cveId": "CVE-2026-123339",
"datePublished": "2026-11-06T14:40:34.836Z",
"dateReserved": "2026-11-05T18:43:28.175Z",
"dateUpdated": "2026-11-06T15:21:40.439Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.