EUVD-2026-75584
GHSA-rf44-j88r-hh8c
Severity by source
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
AC:H because exploitation requires both ForwardAuth middleware and a CGI/WSGI/PHP/NGINX backend simultaneously; PR:L because the attacker must be able to send requests through the Traefik entry point; S:C because identity impact lands on the backend, not Traefik itself.
Primary rating from Vendor (GitHub_M).
CVSS VectorVendor: GitHub_M
Lifecycle Timeline
4DescriptionCVE.org
Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.56, and from 3.0.0 until 3.7.12, a client-supplied dot-form header such as X.Authenticated.User survives ForwardAuth replacement and underscoreHeadersStrategy because Go treats it as distinct from X-Authenticated-User while normalization-prone CGI, WSGI, PHP, and NGINX backends collapse both names. A backend can consequently consume the client value instead of the identity Traefik asserted, allowing identity spoofing for any header managed by Traefik. The aliasHeadersStrategy protection is disabled by default and must be configured as delete or reject. The mitigation is available in 2.11.56 and 3.7.12.
AnalysisAI
ForwardAuth identity spoofing in Traefik allows authenticated network users to impersonate arbitrary identities on normalization-prone backends by sending dot-form HTTP headers (e.g., X.Authenticated.User) that Go's net/http layer treats as distinct from their dash-form equivalents (X-Authenticated-User), while CGI, WSGI, PHP, and NGINX backends collapse both into the same environment variable. Affected deployments span the 2.x branch below v2.11.56 and the 3.x branch from 3.0.0 through 3.7.12; the protective aliasHeadersStrategy option defaults to keep, meaning all unpatched deployments with ForwardAuth and normalization-prone backends are exposed without any additional misconfiguration. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Three conditions must be simultaneously present: (1) Traefik must be configured with the ForwardAuth middleware that asserts an authenticated identity via a response header (e.g., X-Authenticated-User) forwarded to the backend; (2) the backend application must be a normalization-prone runtime - specifically CGI, WSGI, PHP (via $_SERVER), or NGINX (via fastcgi_param or uwsgi_param processing) - that maps header names to environment variables by uppercasing and replacing non-alphanumeric characters with underscores; and (3) the entry point must not have aliasHeadersStrategy configured to delete or reject (the default is keep, so all unpatched deployments meeting conditions 1 and 2 are exploitable with no additional misconfiguration). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The vendor-supplied CVSS 4.0 vector CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N scores 5.3 (Medium). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade to Traefik v2.11.56 (2.x branch) or v3.7.12 (3.x branch) per the tagged releases at https://github.com/traefik/traefik/releases/tag/v2.11.56 and https://github.com/traefik/traefik/releases/tag/v3.7.12. … Detailed patch versions, workarounds, and compensating controls in full report. |
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Same weakness CWE-290 – Authentication Bypass by Spoofing
View allSame technique Authentication Bypass
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External POC / Exploit Code
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