Yesterday afternoon, we released a UEK4 update for both Oracle Linux 6 and Oracle Linux 7.
You can find the announcement mail here.
This update includes a number of generic fixes but most importantly it adds support for retpoline. In order to build this kernel, we also had to release updated versions of gcc which we did a little while ago. You can find more information in general about retpoline on various sites, Here's an article of a discussion on the kernel maillist.
Note, our UEK5 preview kernels (based on 4.14 stable) are also built with retpoline support.
You can find more information about our errata publicly here .