A vulnerability has recently been disclosed in the Linux kernel which affects all systems running CentOS 6. This vulnerability is serious and may allow a remote exploit or local user to cause privilege escalation, resulting in root access to your server. A working example of the exploit has already been publicly disclosed, thus no advanced knowledge of the Linux kernel is required to gain root access once shell access has been obtained on the target system.
The CVE entry for this vulnerability may be found here:
CentOS 5.x is not affected by this vulnerability.
All managed dedicated servers have been automatically upgraded via ksplice. If you have an un-managed server with CentOS 6 and you offer shell access you should upgrade your kernel as soon as possible. If you need any assistance, please open a support ticket.