New versions of postfix, a mail transfer agent, fix two vulnerabilities in older versions of the software. One flaw could be exploited in a denial-of-service (DoS) attack against the affected machine. Another flaw could be exploited to use postfix as a distributed DoS tool for launching attacks against random IP addresses.
Red Hat users, see https://rhn.redhat.com/errata/RHSA-2003-251.html.
Debian users, see http://www.debian.org/security/2003/dsa-363.
SuSE users, see http://www.suse.com/de/security/2003_033_postfix.html.
EnGarde users, see http://www.linuxsecurity.com/advisories/engarde_advisory-3517.html.