After the vulnerability was disclosed earlier this year, Intel released a microcode update to processors Broadwell, Haswell, Skylake, Kaby Lake and Coffee Lake released in the past five years. However, this update was found to cause the system to crash and restart, initially Considered to affect only Broadwell and Haswell processors, however, follow-ups found Skylake, Kaby Lake, and Coffee Lake also have varying degrees of impact.
Intel subsequently advised consumers not to install the update in question. The latest update only applies to Skylake, other processors have to wait.
Reference: security-center.intel.com