The Cisco Wireless LAN Controller (WLC), Cisco Catalyst 6500 Wireless Services Module (WiSM), and Cisco Catalyst 3750 Integrated Wireless LAN Controller with software 4.x before 4.2.176.0 and 5.2.x before 5.2.157.0 allow remote attackers to cause a denial of service (device reload) via a web authentication (aka WebAuth) session that includes a malformed POST request to login.html.