It is possible to limit yum to install only security updates (as opposed to bug fixes or enhancements). To do so, simply install the yum-security plugin:

# yum install yum-security

After installing the yum-security plugin, run the following command to download and install all the available security updates from RHN.

# yum update –security

( formatting errors should show yum update hyphen hyphen security, blame WordPress)

To list all available security updates without installing them, run:

# yum list-security

To list all available security updates with verbose descriptions of the issues they apply to:

# yum info-sec