Dirty COW (CVE-2016-5195) is a privilege escalation vulnerability in the Linux Kernel.
This is an old vulnerability but appears to be something being exploited regularly. In otherwords, keep your stuff up-to-date.
https://github.com/dirtycow/dirtycow.github.io/wiki/VulnerabilityDetails
Check to see if your systems are vulnerable:
https://github.com/dirtycow/dirtycow.github.io/wiki/Check-if-your-system-is-vulnerable