This year saw the discovery of new powerful vulnerabilities in the form of speculative execution: Spectre, Meltdown, and now Foreshadow. These attacks utilize the fact that modern hardware chips will run instructions and only later check whether these should have been carried out. Speculation execution also leaks and provides attackers with new effective side channels that can be used to read secrets. This type of attack is devastating because it means that virtual machines in the cloud can be attacked by other virtual machines running on the same hardware, even when the isolation provided by software layers are perfect.”]
Source: https://www.darkreading.com/cloud/foreshadow-sgx-the-failure-of-trusted-execution