On May 7, Canonical published in a security notice details about a Mesa vulnerability for its Ubuntu 12.04 LTS (Precise Pangolin) operating systems.
According to Canonical, Mesa could have been made to crash, or to run programs, if it processed specially crafted data.
It was discovered that Mesa incorrectly handled certain arrays. An attacker could have used this issue to cause Mesa to crash, resulting in a denial of service, or possibly execute arbitrary code.
The security flaws can be fixed if you upgrade your system(s) to the latest Mesa package. To apply the update, run the Update Manager application.
In general, a standard system update will make all the necessary changes. A system restart will be necessary to implement the changes.
To update your system, please follow these instructions: https://wiki.ubuntu.com/Security/Upgrades.