The Telephony component in Apple iPhone OS 1.0 through 2.2.1 and iPhone OS for iPod touch 1.1 through 2.2.1 allows remote attackers to cause a denial of service (device reset) via a crafted ICMP echo request, which triggers an assertion error related to a "logic issue."
http://www.vupen.com/english/advisories/2009/1621
http://www.securityfocus.com/bid/35414
http://support.apple.com/kb/HT3639
http://lists.apple.com/archives/security-announce/2009/Jun/msg00005.html