Intel prefers to call it is GDS: Gather Data Sampling but Downfall has a better ring to it. Downfall affects the gather instruction with AVX2 and AVX-512 enabled processors. The latest-generation Intel CPUs are not affected but older chips between Tigerlake and Skylake are vulnerable.

Downfall is a vulnerability in the chips memory optimisation feature that unintentionally reveals internal hardware registers to software.

With Downfall, untrusted software can access data stored by other programs that typically should be off-limits: the AVX GATHER instruction can leak the contents of the internal vector register file during speculative execution.

Downfall was discovered by security researcher Daniel Moghimi of Google. Moghimi has written demo code for Downfall to show 128-bit and 256-bit AES keys being stolen from other users on the local system and the ability to steal arbitrary data from the Linux kernel.

Intel acknowledges that their microcode mitigation for Downfall will impact performance where gathering instructions are in an application's hot path. Given the AVX2/AVX-512 impact with vectorization-heavy workloads, HPC workloads will likely be most impacted.

Intel has told its partners that the microcode will have a performance impact up to 50 per cent for workloads with heavy gather instruction use as part of AVX2/AVX-512.

Intel is letting customers know they can disable the microcode change if they feel Downfall will not impact them. Intel believes pulling off a Downfall attack in the real world would be challenging.