Cisco IOS 12.2 12.3 12.4 15.0 and 15.1 when the data-link switching (DLSw) feature is configured allows remote attackers to cause a denial of service (device crash) by sending a sequence of malformed packets and leveraging a \narrow timing window \ aka Bug ID CSCtf74999 a different vulnerability than CVE-2007-0199 CVE-2008-1152 and CVE-2009-0629.