Canonical announced on October 9th, in a security notice, that a new Linux kernel update for its Ubuntu 8.04.4 LTS (Hardy Heron) operating system is available for all users.
There's a single kernel vulnerability, (CVE-2012-2136), discovered by various developers, related to the Linux kernel's network TUN/TAP device implementation.
A local user with access to the TUN/TAP interface (which is not available to unprivileged users until granted by a root user) could have exploited this flaw to crash the system or potential gain administrative privileges.
As usual, you can click on it to see how it affects your system, or go here for in-depth descriptions, as it affects other Linux operating systems as well.
Ubuntu 8.04 LTS users can fix the security flaw if they upgrade to the linux-image-2.6.24-32 package(s).
To apply the update, run the Update Manager application or take a look at some detailed instructions: https://wiki.ubuntu.com/Security/Upgrades.
Don't forget to reboot your computer after the upgrade!