On November 5, Canonical published details about MySQL vulnerabilities for its Ubuntu 12.04 LTS, Ubuntu 11.10, and Ubuntu 10.04 LTS operating systems.
According to Canonical, libproxy could be made to crash or run programs, if it received specially crafted network traffic.
It was discovered that libproxy incorrectly handled certain PAC files. A remote attacker could have used this issue to cause libproxy to crash or to possibly execute arbitrary code, exposing the target.
For a more detailed description of the security problems, you can visit Canonical's security notification
Users can simply fix the security flaws by upgrading the operating systems to the latest libproxy1 package, specific to each distribution.
A normal system update, executed with the Update Manager, will implement all the necessary changes. A complete system restart is not necessary.