This indicates an attempt to exploit a Denial of Service vulnerability in the WireShark SNMP dissector.
The vulnerability is caused by an error in the SNMP dissector. It allows a remote attacker to cause a Denial of Service by crashing the system.
Wireshark (formerly Ethereal) 0.99.6 through 0.99.7.
Denial of Service: remote attackers can crash vulnerable systems.
Update to the latest version 0.99.8, available from the web site: