The 3Com IntelliJack Switch NJ220 before 2.0.23 allows remote attackers to cause a denial of service (reboot and reporting outage) via a loopback packet with zero in the length field.
https://exchange.xforce.ibmcloud.com/vulnerabilities/35172
http://www.vupen.com/english/advisories/2007/2386
http://www.securityfocus.com/bid/24705
http://support.3com.com/infodeli/tools/nj/nj220_02_00_23_readme.pdf