CVE-2026-71325: Traefik: `allowCrossNamespace=false` bypass via `@kubernetescrd` TraefikService backendRef

Severity: medium (CVSS 4.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-06 · updated 2026-09-16
Weakness: CWE-653

Description

Traefik is an open-source edge router that makes publishing services a fun and easy experience. Prior to 2.11.54, 3.6.25, and 3.7.10, cross-namespace @kubernetescrd references are not rejected for TraefikService backend references resolved by the service resolver. A tenant confined by RBAC to a single namespace can therefore bind its own router to a TraefikService owned by another namespace and expose or reroute that namespace's backend, defeating the namespace isolation allowCrossNamespace=false is meant to enforce. This issue is fixed in version 2.11.54, 3.6.25, 3.7.10.

Affected products

Traefik: before 2.11.54; from 3.0.0 before 3.6.25; from 3.7.0 through 3.7.10 — fixed in 2.11.54, 3.6.25

How to fix

Upgrade to a fixed version: Traefik 2.11.54, 3.6.25. Check the vendor advisory for mitigations.

References

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