Canonical announced last evening, September 27, in a security notice, that a new Linux kernel update is now available for its Ubuntu 13.04 (Raring Ringtail) operating system, fixing two security vulnerabilities discovered by various developers in the Linux kernel packages.
You can click on each one to see how it affects your system, or go here for in-depth descriptions, as it affects other Linux operating systems as well.
The security flaws can be fixed if you upgrade your system(s) to the linux-image-3.8.0-31 (3.8.0-31.46) package(s). To apply the update, run the Update Manager application or follow these instructions: https://wiki.ubuntu.com/Security/Upgrades.
Don't forget to reboot your computer after the upgrade!