Kyverno before 1.19.1 Cross-Namespace Data Access via globalcontext.Lib

Kyverno 1.16.0 through 1.19.0 registers the globalcontext.Lib CEL library in its policy environment without confining it to the policy's namespace, unlike the sibling libraries (resource.Lib, http.Lib, configMap loader) which are handed the policy namespace. A tenant who can create a namespaced policy (e.g. NamespacedValidatingPolicy, and likewise the namespaced mutating, deleting, generating, and image-validating policy kinds) in their own namespace can call globalContext.get("<entry>", "") and receive the full cached contents of a cluster-scoped GlobalContextEntry, including data cached from namespaces the tenant has no RBAC permission to read. No admission validation rejects such calls. Fixed in 1.19.1.