NEW SPECTRE-V2 BTR ATTACK LEAKS LINUX MEMORY DESPITE EXISTING DEFENSES

Summary from the TLDR InfoSec newsletter

Researchers from VUSec and Scuola Superiore Sant'Anna disclosed Branch Target Reuse (BTR), a Spectre-v2 variant that reuses stale indirect branch prediction entries in JIT engines after code is freed and reallocated. Proof-of-concept exploits against the Linux cBPF JIT recover the root password hash in minutes on patched Intel systems with default protections. Mitigations are merged in the Linux kernel (CVE-2026-64507, CVE-2026-64508). Mozilla is prioritizing site isolation over IBPB-based fixes.