There are updated samba packages for CentOS 3.3 (and added to 3.1)

https://rhn.redhat.com/errata/RHSA-2004-467.html refers

Updated files are :-

samba-3.0.7-1.3E.i386.rpm samba-client-3.0.7-1.3E.i386.rpm samba-common-3.0.7-1.3E.i386.rpm samba-swat-3.0.7-1.3E.i386.rpm samba-3.0.7-1.3E.i386.rpm

all in updates/i386/RPMS/

These are available at http://mirror.centos.org/3.1/ and should be on all mirrors within a few hours.

To update to the latest version 'yum update samba' should be sufficient.