Last time I checked I was able to install yum-security in CentOS but since it doesn't use the official redhat mirrors I was unable to get it to actually work. Is there a way to make yum-security work or is there an alternative to yum-security on CentOS?
No, there is no easy alternative to this redhat feature with centos.
The only alternative I know so far is to manually list the rpms affected by one or more CVE and update only them.
These days yum-security works fine on CentOS, you can install it from EPEL
Example on CentOS 6:
$ rpm -q yum-plugin-security yum-plugin-security-1.1.30-14.el6.noarch
(On CentOS 5 the package is called yum-security)
$ sudo yum update --security Loaded plugins: security Setting up Update Process Resolving Dependencies Limiting packages to security relevant ones epel/updateinfo | 724 kB 00:00 No packages needed for security; 141 packages available