NetScreen ScreenOS 4.0.1/4.0.3 TCP Window Size Remote Denial of Service Vulnerability

                                                source: http://www.securityfocus.com/bid/8302/info

NetScreen ScreenOS has been reported prone to a vulnerability that may allow a remote user to trigger a denial of service condition in an affected appliance.

It has been reported that by modifying system configuration values that control the TCP window size, an attacker may connect to and trigger a denial of service in an appliance that is running a vulnerable version of ScreenOS.

This issue only affects some ScreenOS 4.0.1rx and 4.0.3rx releases. NetScreen IDP, NetScreen Firewall/VPN products running ScreenOS 3.x and earlier, 4.0.0, and 4.0.2 are not vulnerable. The vendor has supplied upgrades for affected versions.

Modifying registry values on a Windows 2000 system, to reflect the proof of concept below, and connecting to an affected appliance is sufficient to demonstrate the issue:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
New DWORD Value

Tcp1323Opts
HEX
3