In the summer of 2017, two security vulnerabilities were discovered, which went public in January 2018, and caused something of a panic. Meltdown and Spectre, as they were dubbed, did something really nasty. The loopholes were in the very fabric of the microarchitecture, built right into whole families of processors, including every Intel one since 1995 (mostly). A nightmare for the chip makers. Both vulnerabilities exploit speculative execution, including branch prediction, which is as it sounds, where the processor works on data it hasn’t been asked to yet, in the anticipation that it will.
Meltdown works because, as part of the speculative execution, prefetch cache data is not checked for permissions. This opens the door to malicious code getting executed, leading to cache data being open to be read—your password, for…
