Its rare but sometimes it *can* happen. This is an important one to fix! If your running a GNU/Linux server (or desktop), running kernels from 2.6.17 - 220.127.116.11, it is HIGHLY recommended that you update the system using what ever package management system your distro provided, IMMEDIATELY.
If not updated, your system could be at risk allowing a normal shell user to gain root access (i.e root exploit).
A technical overview of the exploit and links to POC code and source code patch can be found here.