COW stands for copy-on-write and it is a mechanism in the Linux Kernel that manages the way modifiable resources are shared among multiple callers. The exploit allows a user to perform privilege escalation and gain root access to the system.

This issue also affects Raspbian (and thus most Raspberry Pi users), but luckily it's easy to Fix the Dirty Cow Exploit on the Raspberry Pi.

Confirm your edition with a simple command.
Ash Ash (357)
2 minutes

So you've got a machine running Ubuntu. If it's been a while since you set up Ubuntu (or maybe you're just curious), you probably need to check what version you're running.