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

RHSA-2005:770-01 Low: libuser security update



Files available:
libuser-0.32-1.el2.1.i386.rpm
libuser-devel-0.32-1.el2.1.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