Black Hat USA 2025 | Racing for Privilege
The main point is that Intel’s modern Spectre v2 defenses, especially eIBRS, can fail because branch predictor updates happen asynchronously. The researchers show that this timing creates “Branch Predictor Race Conditions” (BPRC), where branch predictions can be learned or applied with the wrong privilege context. In practice, that breaks intended isolation boundaries such as user-to-kernel, guest-to-hypervisor, and even barriers meant to flush unsafe predictions. The talk’s key attack is called Branch Privilege Injection (BPI). In plain English: an unprivileged process can trick the CPU into treating attacker-controlled branch…