We present uSpectre, a new class of transient execution attacks that exploit microcode branch mispredictions to transiently leak sensitive data. We find that many long-known and recently-discovered transient execution attacks, which were previously categorized as Spectre or Meltdown variants, are actually instances of uSpectre on some Intel microarchitectures. Based on our observations, we discover multiple new uSpectre attacks and present a defense against uSpectre vulnerabilities, called uSLH.
@article{arxiv.2501.12890,
title = {Analyzing and Exploiting Branch Mispredictions in Microcode},
author = {Nicholas Mosier and Hamed Nemati and John C. Mitchell and Caroline Trippel},
journal= {arXiv preprint arXiv:2501.12890},
year = {2025}
}