CVE-2026-41174: Traefik Kubernetes CRD allows unauthorized cross-namespace middleware binding

Severity: medium (CVSS 6.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-04-30 · updated 2026-06-17
Weakness: CWE-653

Description

Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.43, 3.6.14, and 3.7.0-rc.2, there is a potential vulnerability in Traefik's Kubernetes CRD provider cross-namespace isolation enforcement. When providers.kubernetesCRD.allowCrossNamespace=false, Traefik correctly rejects direct cross-namespace middleware references from IngressRoute objects, but fails to apply the same restriction to middleware references nested inside a Chain middleware's spec.chain.middlewares[]. An actor with permission to create or update Traefik CRDs in their own namespace can exploit this to cause Traefik to resolve and apply middleware objects from another namespace, bypassing the documented isolation boundary. This issue has been patched in versions 2.11.43, 3.6.14, and 3.7.0-rc.2.

Affected products

Traefik: before 2.11.43; from 3.0.0 before 3.6.14; 3.7.0-ea1, 3.7.0-ea2, 3.7.0-ea3, 3.7.0-rc1 — fixed in 2.11.43, 3.6.14

How to fix

Upgrade to a fixed version: Traefik 2.11.43, 3.6.14. Check the vendor advisory for mitigations.

References

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