EUVD-2026-41938Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:L/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
Network vector with low privileges (HTTPRoute creation rights); scope changes to other tenants; high integrity impact via header poisoning; low confidentiality from filter context leakage to attacker.
Primary rating from Vendor (GitHub_M).
CVSS VectorVendor: GitHub_M
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:L/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
Lifecycle Timeline
2DescriptionCVE.org
Traefik is an open source HTTP reverse proxy and load balancer. From v3.7.0 prior to v3.7.6, Traefik's Kubernetes Gateway API provider may resolve two accepted HTTPRoutes that target the same backend Service:port but configure different backendRef filters to the same child service and apply only one route's filter set to all requests reaching that backend. In Gateway deployments where backendRef filters set security-sensitive headers, such as tenant identity, authorization context, or values the backend trusts, an attacker who can create an accepted HTTPRoute sharing the same backend Service:port may cause their route's filter context to be applied to another route's requests, potentially crossing namespace boundaries when a ReferenceGrant permits cross-namespace targeting. This issue is fixed in version v3.7.6.
AnalysisAI
Filter context poisoning in Traefik v3.7.0-v3.7.5 allows a low-privileged Kubernetes user to cause security-sensitive backendRef filters - such as tenant identity or authorization headers trusted by the backend - to be applied to requests from a different, co-located HTTPRoute that targets the same backend Service:port. This affects multi-tenant Kubernetes Gateway API deployments and can cross namespace boundaries when a ReferenceGrant permits cross-namespace backend targeting, making it an authorization bypass and tenant-isolation failure. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires all of the following: Traefik must be deployed with the Kubernetes Gateway API provider (versions 3.7.0-3.7.5); the attacker must hold Kubernetes RBAC permissions sufficient to create an HTTPRoute that is accepted by the Gateway; the attacker's HTTPRoute must target the same backend Service:port as an existing victim route; and the victim route must use backendRef filters to set headers that the backend trusts for authorization or tenant resolution. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The provided CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:N/SC:L/SI:H/SA:N) scores 6.3, capturing that exploitation requires only low privileges with no attack complexity or user interaction, and that the primary harm falls on subsequent systems - other tenants sharing the backend - rather than on Traefik itself. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker with Kubernetes RBAC permissions to create HTTPRoute objects submits a route targeting the same backend Service:port as a legitimate tenant's route, configuring a backendRef filter that sets a header such as X-Tenant-ID to the attacker's own tenant value. Due to the filter resolution bug, Traefik applies the attacker's filter set to the legitimate tenant's requests as well, causing the backend to process those requests under the wrong tenant identity - potentially granting unauthorized access to another tenant's data. … |
| Remediation | Upgrade Traefik to v3.7.6, which resolves the filter resolution logic (upstream fix: commit 8aada7a7d52e4588a75386d8b86d270f6fe8d549, PR #13367 at https://github.com/traefik/traefik/pull/13367; release confirmed at https://github.com/traefik/traefik/releases/tag/v3.7.6). … Detailed patch versions, workarounds, and compensating controls in full report. |
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External POC / Exploit Code
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