Updated libtiff packages are available for CentOS-3
libtiff: https://rhn.redhat.com/errata/RHSA-2004-577.html
i386/RPMS/libtiff-3.5.7-20.1.i386.rpm
i386/RPMS/libtiff-devel-3.5.7-20.1.i386.rpm
i386/SRPMS/libtiff-3.5.7-20.1.src.rpm
All of these updates can be applied by running the command:
yum update