It can be hard to keep track of legacy systems, and they may be excluded from patching due to compatibility issues with certain services or applications.
Note: Kernel exploits can cause system instability so use caution when running these against a production system.
Exploitation
uname -a
search the kernel version for any exploits, copy and run them
cat /lsb-release
id the os version
Linux Kernel 4.4.0-116 on an Ubuntu 16.04.4 LTS box
google searching the above line for an exploit
https://vulners.com/zdt/1337DAY-ID-30003
OR LOOK for the specific OS version / kernel version here - https://github.com/JlSakuya/Linux-Privilege-Escalation-Exploits