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?
Unfortunately, yum-security is not supported on CentOS :(
However, this hacked alternative might work for you.
These days yum-security works fine on CentOS, you can install it from EPEL
Example on CentOS 6:
(On CentOS 5 the package is called yum-security)