CentOS Errata and Security Advisory 2007:0358
https://rhn.redhat.com/errata/RHSA-2007-0358.html
The following updated files have been uploaded and are currently syncing to the mirrors:
i386: squirrelmail-1.4.8-4.0.1.el4.centos.noarch.rpm
src: squirrelmail-1.4.8-4.0.1.el4.centos.src.rpm