ZombieLoad: Cross Privilege-Boundary Data Leakage on Intel CPUs

When the operating system schedules two threads from completely different applications on the logical cores of the same physical core, data of both applications is processed at the same time in the shared execution resources. It turns out that on Intel processors this wrong data may be data from outside the current process but still loaded by the physical CPU core for whatever reason, which can be:

An important detail is that the attacker has no direct control over what data is read here. In this scenario, the attacker executes unprivileged code on one logical CPU core, while a victim application runs on the other logical (but same physical) core.

Source: www.cyberus-technology.de