If you aren’t aware – a bug that has persisted for over a decade has come to light with how speculative branching in CPUs (not only Intel, writers) can lead to people able to access others’ volatile data in kernelspace.

What this means, essentially, is that any multiuser system is inherently insecure for any local user access. This is not a good thing.

Patches have been made against the most recent Linux kernels, and should be installed!

If you are running debian stretch, for example, here’s a simple way to get “up to date” with the debian security branch (assuming you are running x86_64):

$sudo $SHELL
#echo 'deb http://security.debian.org/debian-security stretch/updates \
  main contrib non-free' >> /etc/apt/sources.list
#apt-get update
#apt-get install linux-image-4.9.0-5-amd64 iucode-tool
#wget http://ftp.us.debian.org/debian/pool/non-free/i/intel-microcode/\
intel-microcode_3.20171215.1_amd64.deb
#dpkg -i intel-microcode_3.20171215.1_amd64.deb && rm \
  intel-microcode_3.20171215.1_amd64.deb
#reboot

What this does is add debian-security to your apt sources, update the list, install the latest (stock) 4.9.x kernel with the patches against Meltdown, and install a current microcode patch – which only supports a few processors right now, but will likely be updated, so a subsequent update should pull in any future firmware patches.

Of course, this assumes a stock kernel/Debian 9 configuration. If you’re using stretch-backports, there is not yet a 4.14 release available with patches at the time of this post.