The L2TP protocol parser in tcpdump 3.8.1 and earlier allows remote attackers to cause a denial of service (infinite loop and memory consumption) via a packet with invalid data to UDP port 1701, which causes l2tp_avp_print to use a bad length value when calling print_octets.
http://www.securitytracker.com/id?1008748
http://www.securityfocus.com/archive/1/350238/30/21640/threaded
http://www.mandriva.com/security/advisories?name=MDKSA-2004:008
http://www.debian.org/security/2004/dsa-425
http://secunia.com/advisories/10718
http://secunia.com/advisories/10668
http://secunia.com/advisories/10652
http://secunia.com/advisories/10636
http://marc.info/?l=tcpdump-workers&m=107228187124962&w=2
http://marc.info/?l=bugtraq&m=107213553214985&w=2