Disclosure of the nine-year-old vulnerability came the same week that Google researcher Kees Cook published research showing that the average lifetime of a Linux bug is five years.

"The systems using a Linux kernel are right now running with security flaws," Cook wrote. "Those flaws are just not known to the developers yet, but they’re likely known to attackers."
http://arstechnica.com/security/2016/10/most-serious-linux-privilege-escalation-bug-ever-is-under-active-exploit/#p3