Speculative Store Bypass (SSB) (CVE-2018-3639) is the name given to a hardware security vulnerability and its exploitation that takes advantage of speculative execution in a similar way to the Meltdown and Spectre security vulnerabilities.
It was discovered by researchers at Microsoft Security Response Center and Google Project Zero (GPZ).
[7] Intel said in a statement that the likelihood of end users being affected was "low" and that not all protections would be on by default due to some impact on performance.
[10] The Chrome JavaScript team confirmed that effective mitigation of Variant 4 in software is infeasible, in part due to performance impact.
[11] Intel is planning to address Variant 4 by releasing a microcode patch that creates a new hardware flag named Speculative Store Bypass Disable (SSBD).