Intel processors (speculative store bypass): Spectre v4: a load speculatively executes before an older store

Impact

Spectre v4: a load speculatively executes before an older store to the same address is resolved, so it reads stale data. The exposure that matters is inside language runtimes and sandboxes where the attacker supplies the code being JITed - which describes most of a model-serving stack.

Who can reach it

Local code execution, including inside sandboxes and JIT runtimes.

What to do

Mitigated by an Intel microcode update plus OS/hypervisor changes. Microcode for this class is normally shipped by your distribution as an early-loadable image, so you can deploy it with a package update and a reboot without waiting for an OEM BIOS release - that distinction is the difference between a week and a quarter. Verify after reboot by reading /sys/devices/system/cpu/vulnerabilities/ rather than assuming the package took effect. The mitigation (SSBD) is opt-in per process on Linux because it costs measurable performance; decide deliberately whether your JIT-hosting workloads get it via prctl or whether you enable it system-wide.

References