how to get package update availaibilty

Hello,

I am running RHEL6.3 on HP Blade servers. These servers are not connected with RHN network as it's production servers and connectivity to outer network is blocked.

Now I have the list of packages installed on my server with rpm -qa but i want to know which of these package have latest updates and if any package has any security vulnerability.

Appreciate any help how to find this.