This guide explains how to update Ruby in case you installed it from source according to the instructions in https://gitlab.com/gitlab-org/gitlab-ce/blob/masterdoc/install/installation.md#2-ruby .
Find the latest stable version of Ruby 1.9 or 2.0 at https://www.ruby-lang.org/en/downloads/ . We recommend at least 2.0.0-p353, which is patched against [CVE-2013-4164](https://www.ruby-lang.org/en/news/2013/11/22/heap-overflow-in-floating-point-parsing-cve-2013-4164/).
Just to be sure we will reinstall the gems used by GitLab. Note that the `bundle install` command [depends on your choice of database](https://gitlab.com/gitlab-org/gitlab-ce/blob/masterdoc/install/installation.md#install-gems).