The following errata for CentOS-2 have been built and uploaded to the centos mirror:
RHSA-2008:0988-01 Important: libxml2 security update
Files available: libxml2-2.4.19-12.ent.i386.rpm libxml2-devel-2.4.19-12.ent.i386.rpm libxml2-python-2.4.19-12.ent.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