The Teredo implementation in Microsoft Windows Vista uses the same nonce for communication with different UDP ports within a solicitation session, which makes it easier for remote attackers to spoof the nonce through brute force attacks.
osvdb.org/33666
www.securityfocus.com/archive/1/462793/100/0/threaded
www.securityfocus.com/archive/1/464617/100/0/threaded
www.securityfocus.com/bid/23301
www.symantec.com/avcenter/reference/Vista_Network_Attack_Surface_RTM.pdf
www.symantec.com/enterprise/security_response/weblog/2007/04/microsofts_inaccurate_teredo_d.html