Intel has had quite a lot of work trying to patch all vulnerabilities discovered in the past two years. Starting from Spectre and Meltdown which exploited speculative execution of the processor to execute malicious code. The entire process of speculative execution relies on the microarchitectural technique for adding more performance called speculative branch prediction. This technique predicts branch paths and prepared them for execution, so the processor spends less time figuring out where and how will instructions flow through the CPU. So far, lots of these bugs have been ironed out with software, but a lot of older CPUs are vulnerable.

However, an attacker has always thought about doing malicious code execution on a CPU core shared with the victim, and never on multiple cores. This is where the new CrossTalk vulnerability comes in. Dubbed Special Register Buffer Data Sampling (SRBDS) by Intel, it is labeled as CVE-2020-0543 in the vulnerability identifier system. The CrossTalk is bypassing all intra-core patches against Spectre and Meltdown so it can attack any CPU core on the processor. It enables attacker-controlled code execution on one CPU core to leak sensitive data from victim software executing on a different core. This technique is quite dangerous for users of shared systems like in the cloud. Often, one instance is shared across multiple customers and until now they were safe from each other. The vulnerability uses Intel's SGX security enclave against the processor so it can be executed. To read about CrossTalk in detail, please visit the page here.