Dirty COW is an underlying issue was a race condition in the way kernel handles copy-on-write (COW).
More information can be found on CVE-2016-5195.
To find out if your server is affected, check your kernel version.
uname -rv
You'll see output like this:
Output
4.4.0-42-generic #62-Ubuntu SMP Fri Oct 7 23:11:45 UTC 2016
If your version is earlier than the following, you are affected:
sudo apt-get update && sudo apt-get dist-upgrade
<WRAP info> On Redhat use:
sudo yum update kernel </code>
Then reboot.