CentOS Errata and Security Advisory 2006:0543
https://rhn.redhat.com/errata/RHSA-2006-0543.html
The following updated files have been uploaded and are currently syncing to the mirrors:
s390: updates/s390/RPMS/spamassassin-3.0.6-1.el4.s390.rpm
s390x: updates/s390x/RPMS/spamassassin-3.0.6-1.el4.s390x.rpm