Dirty COW (CVE-2016-5195) is a privilege escalation vulnerability that Linux Kernel has and exists since 2005. CVE stands for Common Vulnerabilities and Exposures).
The explanation why this can be referred as Dirty COW is as a result of a race condition that was found in Linux kernels memory subsystem, handled the copy-on-write (COW) breakage of private read-only memory mappings. That means that a local user that did not have the privilege, could use this flaw for gaining access to read only memory mappings. That would end up as a result that their privileges on the system would be increased. This vulnerability is already fixed though, for both Debian or Ubuntu but only for the users that are up to date with their updates.
So if for some reason you’re not, here is the way to fix and patch Linux Kernel from Dirty COW CVE-2016-5195)
Debian or Ubuntu dirty COW fix:
$ sudo apt-get update && sudo apt-get upgrade && sudo apt-get dist-upgrade $ sudo reboot
RHEL / CentOS Linux 5.x/6.x/7.x dirty COW fix:
$ sudo yum update $ sudo reboot