CVE-2026-54523: cross-namespace escalation Kyverno 1.18.0

CVE-2026-54523 is a critical vulnerability in Kyverno, a policy engine for cloud-native Kubernetes platforms, in versions from 1.18.0 onward: the CEL compiler in NamespacedMutatingPolicy exposes the generator library to matchConditions, allowing a namespace-scoped policy to execute generator.apply() with an arbitrary target namespace. Kyverno's admission controller, operating with cluster-wide privileges, does not properly enforce the original namespace scope, allowing resource creation in unauthorized namespaces.

Severity is maximum (CVSS 9.6, critical). A user who can create NamespacedMutatingPolicy in a single namespace can induce the controller to generate ConfigMaps, Secrets, RoleBindings, NetworkPolicies and other resources in different and unauthorized namespaces. In multi-tenant environments, this enables privilege escalation and uncontrolled resource modification across the cluster with the same permissions as the controller (cluster-wide). The flaw was documented on August 26, 2026; social signals in late October 2026 indicate public awareness of the vulnerability.

Kubernetes administrators must update Kyverno to version 1.18.2 or later without delay. Verify version with 'kyverno version'; if version is from 1.18.0 through versions before 1.18.2, plan immediate update. Check RBAC to restrict NamespacedMutatingPolicy creation to system admins only, not tenants. Enable audit logging for policy-create events in non-admin namespaces and monitor anomalous cross-namespace Secrets and RoleBindings creation as exploitation indicator.

Validation in the CEL compiler (pkg/cel/policies/mpol/validate.go) and in GenerateResources (pkg/cel/libs/context.go) was strengthened in version 1.18.2 to enforce namespace scope and reject cross-namespace targets. No known workarounds exist other than upgrading.