Format string vulnerabilities in the (1) die or (2) log_event functions for ssmtp before 2.50.6 allow remote mail relays to cause a denial of service and possibly execute arbitrary code.
https://exchange.xforce.ibmcloud.com/vulnerabilities/15872
http://www.securityfocus.com/bid/10150
http://www.debian.org/security/2004/dsa-485
http://securitytracker.com/id?1009788
http://security.gentoo.org/glsa/glsa-200404-18.xml
http://secunia.com/advisories/11571
http://secunia.com/advisories/11485
http://secunia.com/advisories/11384