In OpenStack Cyborg before 16.0.1, the Accelerator Request (ARQ) API does not enforce project ownership at any layer. The project_id column in the database is never populated (NULL for every ARQ), database queries have no project filtering, and policy checks are self-referential (the authorize_wsgi decorator compares the caller's project_id with itself rather than the target resource). Any authenticated non-admin user can complete various actions such as deleting ARQs bound to other projects' instances, aka cross-tenant denial of service.