Intel processors (snoop-assisted L1D sampling): Data can be leaked out of L1D during snoop transactions, crossing

Impact

Data can be leaked out of L1D during snoop transactions, crossing privilege boundaries. Lower practical yield than the fill-buffer attacks but it targets the same shared L1 that makes SMT co-tenancy risky.

Who can reach it

Local code on the same physical core as the victim.

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.

References