All the media has talked about it…On October 19, 2016, a privilege escalation vulnerability in the Linux kernel was disclosed under the name of Dirty COW. A 9 years old vulnerability…(With the kernel 2.6.22) impacting a large number of Linux servers.
So what is it and how to fix it?
The issue come from how the kernel handles Copy-On-Write (COW, so, nothing about cows).
It is basically a privilege-escalation bug. This vulnerability allows for escalating the privilege of a user space process, granting it super user privileges. Users can gain write-access to memory mappings that are normally set to read-only.
Very dangerous then!
Fixing it should be straightforward as most distributions have released a fix, in a new kernel.
You should still check for your kernel version:
If your version is earlier than the following, you are affected:
• 4.8.0-26.28 for Ubuntu 16.10
• 4.4.0-45.66 for Ubuntu 16.04 LTS
• 3.13.0-100.147 for Ubuntu 14.04 LTS
• 3.2.0-113.155 for Ubuntu 12.04 LTS
• 3.16.36-1+deb8u2 for Debian 8
• 3.2.82-1 for Debian 7
• 4.7.8-1 for Debian unstable
If it is the case, you should immediately update your system:
sudo apt-get update && sudo apt-get dist-upgrade
And then make sure it has upgraded your kernel.
If done, simply reboot your system to boot on the new kernel.