unzoo.c, as used in multiple products including AMaViS 2.4.1 and earlier, allows remote attackers to cause a denial of service (infinite loop) via a ZOO archive with a direntry structure that points to a previous file.
https://exchange.xforce.ibmcloud.com/vulnerabilities/34080
http://www.securityfocus.com/archive/1/467646/100/0/threaded
http://www.amavis.org/security/asa-2007-2.txt
http://securityreason.com/securityalert/2680