https://arstechnica.com/gadgets/2018/01/meltdown-and- spectre-every-modern- processor-has-unfixable- security-fladdws/U
TL;DR
Windows, Linux, and macOS have all received security patches that
significantly alter how the operating systems handle virtual memory in
order to protect against a hitherto undisclosed flaw.
Debian does not have this released as a kernel update yet in any release at this time.
https://security-tracker.debian.org/tracker/CVE-2017-5754