Googles Project Zero team posted detailed technical information on three variants of a new security issue involving speculative execution on many modern CPUs. Google developed a novel mitigation called Retpoline — a binary modification technique that protects against branch target injection attacks. We have deployed it on Google’s systems, where we have observed negligible impact on performance. Google recommends thorough testing in your environment before deployment; we cannot guarantee any particular performance or operational impact. Variant 1 allows malicious code to circumvent bounds checking features built into most binaries. Variant 2 allows an attacker to use the ability of speculative execution behavior of one process to influence the behavior of another.”]
Source: https://security.googleblog.com/2018/01/more-details-about-mitigations-for-cpu_4.html