Postfix 2.1.3, when /proc/net/if_inet6 is not available and permit_mx_backup is enabled in smtpd_recipient_restrictions, allows remote attackers to bypass e-mail restrictions and perform mail relaying by sending mail to an IPv6 hostname.
bugs.debian.org/cgi-bin/bugreport.cgi?bug=267837
marc.info/?l=bugtraq&m=110763358832637&w=2
secunia.com/advisories/14137/
www.redhat.com/support/errata/RHSA-2005-152.html
www.securityfocus.com/bid/12445
exchange.xforce.ibmcloud.com/vulnerabilities/19218
oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A11339