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.