On December 17, Canonical published in a security notice details about a bogofilter vulnerability for its Ubuntu 10.04 LTS (Lucid Lynx) operating systems.
According to Canonical, bogofilter could have been made to crash or run programs, if it processed a specially crafted email.
It was discovered that bogofilter incorrectly handled certain invalid base64 code. By sending a specially crafted email, a remote attacker could have exploited this issues and cause bogofilter to crash, resulting in a denial of service, or possibly execute arbitrary code.
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 bogofilter-bdb and bogofilter-sqlite packages.
A normal system update, executed with the Update Manager, will implement all the necessary changes. A complete system restart is not necessary.