EUVD-2026-41938
GHSA-6p8f-p8j2-rqmv
Severity 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
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. No public exploit identified at time of analysis; the issue is fixed in Traefik v3.7.6.
Technical ContextAI
Traefik's Kubernetes Gateway API provider processes HTTPRoutes and resolves their backendRef filters - middleware-level header transformations applied per route - to backend Service:port pairs. The root cause (CWE-284: Improper Access Control) is that when two accepted HTTPRoutes resolve to the same backend Service:port but declare distinct backendRef filter sets, Traefik collapses them to a single child service entry and applies only one route's filter set to all traffic reaching that backend. The affected CPE is cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:* for versions 3.7.0 through 3.7.5. This vulnerability is specific to the Kubernetes Gateway API provider and does not affect Traefik's IngressRoute CRD or legacy Ingress providers.
RemediationAI
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). For deployments unable to upgrade immediately, restrict Kubernetes RBAC so that only trusted administrators can create or modify HTTPRoute objects in namespaces that target security-sensitive backends - this eliminates the ability of low-privileged users to introduce conflicting routes and is a high-efficacy compensating control, though it conflicts with self-service multi-tenant provisioning models. Additionally, audit all ReferenceGrant objects to ensure cross-namespace backend targeting is scoped to explicitly authorized namespace pairs, reducing the blast radius of cross-tenant filter poisoning. Deployments that do not use backendRef filters to set security-sensitive headers are not exposed and do not require emergency action.
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Same weakness CWE-284 – Improper Access Control
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View allVendor StatusVendor
SUSE
Severity: Important| Product | Status |
|---|---|
| openSUSE Tumbleweed | Fixed |
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