On October 10th, in a security notice Canonical published details about Ruby 1.8 vulnerabilities for its Ubuntu 12.04 LTS, Ubuntu 11.10, Ubuntu 11.04, and Ubuntu 10.04 LTS operating systems.
According to Canonical, Ruby 1.8 could have allowed excessive access in untrusted programs. Shugo Maedo and Vit Ondruch discovered that Ruby 1.8 incorrectly allowed untainted strings to be modified in protective safe levels.
An attacker could have used this flaw in Ruby 1.8 in order to bypass intended access restrictions.
The security flaws can be fixed if you upgrade your system(s) to the latest Ruby 1.8 package, specific to each operating system. To apply the update, run the Update Manager application.
In general, a standard system update will make all the necessary changes. A system restart won't be necessary to implement the changes.