Kong Mesh multi-zone: the global control plane attributes KDS-synced resources by an unvalidated in-band zone identifier

On a Kong Mesh global control plane, resources received over the zone-to-global KDS sync are attributed using the in-band, sender-controlled ControlPlane.Identifier rather than the authenticated zone identity derived from the connection. Authenticated zones can have the global control plane store and re-distribute those resources as belonging to another zone. The result is a cross-zone isolation bypass: the holder of a single enrolled zone's credential can inject, attribute, and overwrite resources in another zone's namespace mesh-wide. The root cause lives in Kuma's open-source KDS sync code, which Kong Mesh's control plane is built on.