http://arstechnica.com/security/2015...linux-systems/
http://www.zdnet.com/article/critica...ty-hole-found/
Basically this bug makes it possible to remotely gain access to a Linux server by exploiting this bug, although a service needs to be running on the server which uses the function that contains the bug, you never know what service/software uses this.
You can test if you're vulnerable with this
http://security.stackexchange.com/a/80213
Be sure to patch your VPS/dedicated server.
How to patch.
In case you use shared hosting, inform your host and ask them if they patched it or if they can patch it asap.