COMMAND

    telnetd

SYSTEMS AFFECTED

    Microsoft Windows 2000 Telnet Server

PROBLEM

    Following  is  based  on  FSC  Internet/SecureXpert Labs Advisory.
    Microsoft Windows  2000 Server  is supplied  with a  Telnet server
    for  remote  console  access.   A  Denial of Service vulnerability
    exists in this server which may be exploited by a local or  remote
    attacker.

    A remote user  can cause the  telnet server to  stop responding to
    requests by sending a stream of binary zeros to the telnet server.
    This can  easily be  reproduced from  a Linux  system using netcat
    with an input of /dev/zero, with a command such as

        nc target.host 23 < /dev/zero

    The Windows 2000 Telnet Server stops responding to requests  after
    a  few  seconds.   If  the  Telnet  Server  is set to restart upon
    failure, it will  restart and immediately  fail.  This  will occur
    repeatedly until the Telnet  Server exceeds its restart  count, at
    which point the service remains down.

SOLUTION

    Patch availability:

        - Microsoft Windows 2000 All Versions: http://www.microsoft.com/Downloads/Release.asp?ReleaseID=22753