Cross-tenant exposure is a failure in shared infrastructure where data from one customer becomes visible to another. It can happen in clouds, hosted containers, virtualized storage, or other multi-tenant systems when isolation controls fail at a layer below the application. Unlike a classic account takeover, the attacker may not need valid access to the victim’s tenant; the weakness is in how the provider separates customers.
This matters because it can reveal sensitive content even when authentication, permissions, and network segmentation are working correctly. In practice, exposure often comes from stale data, reused storage blocks, misrouted logs, or control-plane bugs. Defenses include strong tenant isolation, block zeroing before reuse, encrypted storage, strict access boundaries, and testing that checks for residual data across tenant transitions. Security teams treat cross-tenant exposure as a confidentiality failure, because one broken shared layer can leak many customers’ data at once.