Ubuntu Security team announced a major security alert to users of Ubuntu On February 5th .The security flaw is found in the kernel of the different versions of Ubuntu. This makes it vulnerable to the system, allowing the escalation of privileges and gain control of the system by an attacker.
List of affected Ubuntu releases:
Ubuntu 6.06 LTS Ubuntu 6.06 LTS
Ubuntu 8.04 LTS Ubuntu 8.04 LTS
Ubuntu 8.10 Ubuntu 8.10
Ubuntu 9.04 Ubuntu 9.04
Ubuntu 9.10 Ubuntu 9.10
It is important to resolve it, update your kernel to the latest version available. Something that many have already done but it is worth remembering. The importance of this fact is not in the bug is. It is in how fast it is resolved and as the user community has turned to communicate in all media achievable.
More info : Ubuntu Security Notice USN-894-1