Cisco PIX firewall 5.x.x, and 6.3.1 and earlier, allows remote attackers to cause a denial of service (crash and reload) via an SNMPv3 message when snmp-server is set.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2003-0993
http://www.cisco.com/warp/public/707/cisco-sa-20031215-pix.shtml