CVE-2026-71193: falha crítica em OpenStack Designate

In OpenStack Designate before 22.0.1, zone creation checks (_is_subzone, _is_superzone, and the duplicate-zone DB constraint) are scoped to the target pool only. An authenticated user can bypass these checks by scheduling a zone to a different pool via the AttributeFilter scheduler, creating an overlapping zone that conflicts with another tenant's zone. This enables cross-tenant DNS hijack (redirecting traffic to attacker-controlled IPs) and DNS denial of service (NODATA responses). Exploitation requires a multi-pool deployment with AttributeFilter enabled in scheduler_filters, which is a non-default but documented and supported configuration for self-service tiering.