The following errata for CentOS-2 have been built and uploaded to the centos mirror:

RHSA-2006:0498-01 Moderate: xscreensaver security update

Files available:
xscreensaver-3.33-4.rhel21.3.i386.rpm

More details are available from the RedHat web site at
https://rhn.redhat.com/errata/rh21as-errata.html

The easy way to make sure you are up to date with all the latest patches is to run:
# yum update