CentOS 5.11 is the distribution's final release in the 5.x branch. CentOS 5.11 is based on source code released by Red Hat, Inc. and it includes packages from all variants, including Server and Client. The Bash version included on the CentOS 5.11 ISO images is a version that contains the shellshock vulnerability.
About CentOS
CentOS as a group is a community of open source contributors and users. Typical CentOS users are organisations and individuals that do not need strong commercial support in order to achieve successful operation. CentOS is 100% compatible rebuild of the Red Hat Enterprise Linux, in full compliance with Red Hat's redistribution requirements. CentOS is for people who need an enterprise class operating system stability without the cost of certification and support.