Updated gd packages are avaiable for CentOS-2
The following errata for CentOS-2 have been built and uploaded the the centos mirror:
RHSA-2004:638-01 Updated gd packages fix security issues
Files available:
gd-1.8.4-4.21.1.i386.rpm
gd-devel-1.8.4-4.21.1.i386.rpm
gd-progs-1.8.4-4.21.1.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