Topic
Security of just-in-time compilation engines, which generate and replace machine code at runtime in browsers, language runtimes and kernels.
Intel, AMD and Arm say their IBPB barrier can block Branch Target Reuse, a Spectre v2 variant hitting all three, if JIT software calls it. Each kernel, browser and runtime that rewrites JIT code now has to add that call itself.
Reality
Linux has merged two kernel fixes, CVE-2026-64507 and CVE-2026-64508, for the Branch Target Reuse Spectre-v2 variant that leaks memory through JIT engines. GraalVM and Firefox took other routes, so a host's coverage depends on which JIT engine it lets untrusted code run in.
Reality
VUsec and Sant'Anna researchers built BTR, a Spectre v2 variant that read a Linux root password hash off two Intel cores in three to five minutes. The Linux kernel fix is merged, and the researchers advise applying operating system and firmware updates.
Reality