Security researchers from Graz University of Technology imec-DistriNet, and College of William and Mary have discovered seven new CPU attacks, which impact AMD, ARM, and Intel CPUs.

In their paper, the researchers present "a sound and extensible systematization of transient execution attacks" -- a term the research team used to describe attacks on the various internal mechanisms that a CPU uses to process data. Their systematization uncovered 7 new transient execution attacks that have been overlooked and not been investigated so far. This includes 2 new Meltdown variants: Meltdown-PK on Intel (bypasses memory protection keys on Intel CPUs), and Meltdown-BR on Intel and AMD (exploits an x86 bound instruction on Intel and AMD). It also includes 5 new Spectre mistraining strategies.

The researchers evaluated all 7 attacks in proof-of-concept implementations on 3 major processor vendors (Intel, AMD, ARM). Experiments to confirm six other Meltdown-attacks did not succeed, according to the researchers.

Through their systematic evaluation, they discovered that transient execution attacks that are supposed to be mitigated by rolled out patches can be still mounted.

The research team says they reported all their findings to the three CPU vendors whose processors they've analyzed, but that only ARM and Intel acknowledged their findings.