MadWifi, when Ad-Hoc mode is used, allows remote attackers to cause a denial of service (system crash) via unspecified vectors that lead to a kernel panic in the ieee80211_input function, related to "packets coming from a 'malicious' WinXP system."
http://www.ubuntu.com/usn/usn-479-1
http://www.securityfocus.com/bid/23433
http://www.securityfocus.com/archive/1/466689/30/6900/threaded
http://www.novell.com/linux/security/advisories/2007_14_sr.html
http://www.mandriva.com/security/advisories?name=MDKSA-2007:082
http://secunia.com/advisories/26083
http://secunia.com/advisories/25861