GEN:SID 1:1939
Message MISC bootp hardware address length overflow
Summary This event is generated when a possible buffer overflow is attempted for the bootpd service.
Impact Remote access. This attack may permit the execution of arbitrary commands on the vulnerable server.
Detailed Information Bootp is a protocol used for devices such as diskless workstations to locate a host from which to boot and to receive an assigned an IP address.  A flaw exists in the bootpd service allowing a possible buffer overflow condition when a bootp request is issued with an invalid hardware address type. This attack may permit the execution of arbitrary commands on the vulnerable server.
Affected Systems OpenBSD 2.3, 2.4
FreeBSD - Releases up to and including 2.x
Attack Scenarios An attacker may attempt to use this exploit to gain remote access on the vulnerable server.
Ease of Attack Simple. Exploit code is freely available.
Corrective Action Block bootp traffic from entering your network.  
Additional References CVE
http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-1999-0798
Rule References cve: 1999-0798