Bitdefender senior researchers Dan Horea Luțaș and Andrei Vlad Luțaș recently uncovered a new speculative-execution vulnerability and demonstrated how it can be exploited via a side-channel style attack, dubbed SWAPGS Attack.
Affects Intel processors from Ivy Bridge onwards. AMD have issued a statement claiming that they are not affected because "AMD products are designed not to speculate on the new GS value following a speculative SWAPGS".
Fixed by the following kernel releases:
See also https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=18ec54f.