The VLAN Trunking Protocol (VTP) feature in Cisco IOS 12.1(19) allows remote attackers to cause a denial of service by sending a VTP version 1 summary frame with a VTP version field value of 2.
secunia.com/advisories/21896
securitytracker.com/id?1016843
www.cisco.com/warp/public/707/cisco-sr-20060913-vtp.shtml
www.kb.cert.org/vuls/id/821420
www.osvdb.org/28775
www.phenoelit.de/stuff/CiscoVTP.txt
www.securityfocus.com/archive/1/445896/100/0/threaded
www.securityfocus.com/archive/1/445938/100/0/threaded
www.securityfocus.com/bid/19998
www.vupen.com/english/advisories/2006/3600
exchange.xforce.ibmcloud.com/vulnerabilities/28924