The SSHv2 implementation in Cisco IOS 12.2, 12.4, 15.0, 15.1, and 15.2 and IOS XE 2.3.x through 2.6.x and 3.1.xS through 3.4.xS before 3.4.2S allows remote attackers to cause a denial of service (device reload) via a crafted username in a reverse SSH login attempt, aka Bug ID CSCtr49064.