  Microarchitectural Data Sampling (MDS) is a set of hardware vulnerabilities
in Intel CPUs that allows an attacker to leak bytes of data from memory loads
and stores across various security boundaries. On affected CPUs, some of these
vulnerabilities were patched via microcode updates. Additionally, Intel
announced that the newest microarchitectures, namely Cascade Lake and Ice Lake,
were not affected by MDS. While Cascade Lake turned out to be vulnerable to the
ZombieLoad v2 MDS attack (also known as TAA), Ice Lake was not affected by this
attack.
  In this technical report, we show a variant of MSBDS (CVE2018-12126), an MDS
attack, also known as Fallout, that works on Ice Lake CPUs. This variant was
automatically synthesized using Transynther, a tool to find new variants of
Meltdown-type attacks. Based on the findings of Transynther, we analyze
different microcodes regarding this issue, showing that only microcode versions
after January 2020 prevent exploitation of the vulnerability. These results
show that Transynther is a valuable tool to find new variants, and also to test
for regressions possibly introduced with microcode updates.
