gdb security update for CentOS 3 x86_64:
https://rhn.redhat.com/errata/RHSA-2007-0469.html

The following updated file has been uploaded and is currently syncing to the mirrors:

x86_64:
updates/x86_64/RPMS/gdb-6.3.0.0-1.138.el3.i386.rpm
updates/x86_64/RPMS/gdb-6.3.0.0-1.138.el3.x86_64.rpm

source:
updates/SRPMS/gdb-6.3.0.0-1.138.el3.src.rpm

You may update your CentOS-3 x86_64 installations by running the command:

yum update gdb