Microsoft Security Bulletin (MS00-020)
Patch Available for "Desktop Separation" Vulnerability
Originally Posted: June 15, 2000
Microsoft has released a patch that eliminates a security
vulnerability in Microsoft(r) Windows(r) 2000. The vulnerability
could allow a malicious user to gain additional privileges on a
machine that he could log onto at the keyboard.
Frequently asked questions regarding this vulnerability
can be found at
In the Windows 2000 security model, a hierarchy of container objects
is used to separate processes. Every session contains one or more
windows stations; every windows station contains one or more desktops.
By design, processes are constrained to run within a windows station,
and the threads in the process run in one or more desktops. A process
in one windows station should not be able to access desktops
belonging to another windows station. However, due to an
implementation error, this could happen under very specific
circumstances. This could allow a process belonging to a low-privilege
user to view inputs or output that belong to another desktop within
the same session, and potentially obtain information such as
The vulnerability only affects desktops within the same session. As a
result, a malicious user could only interfere with processes on the
same local machine, and only if he could interactively log onto it.
Security best practices strongly militate against allowing normal
users to interactively log onto security-sensitive servers, and if
this practice has been followed, machines such as domain controllers,
print and file servers, ERP servers, database servers, and others
would not be at risk. In addition, other security best practices, if
followed, would prevent a malicious user from launching the processes
in a way that allows them to exploit this vulnerability. Windows 2000
Terminal Servers are not affected by this vulnerability, because
every user runs in his own session.
Affected Software Versions
- Microsoft Windows 2000 Professional
- Microsoft Windows 2000 Server
- Microsoft Windows 2000 Advanced Server
Note: Due to a known compatibility error, the patch should not be
applied to clustered Windows 2000 systems that are administered via
the Microsoft Management Console.
Note: Additional security patches are available at the Microsoft
Please see the following references for more information related to
- Microsoft Security Bulletin MS00-020: Frequently Asked Questions,
- Microsoft Knowledge Base (KB) article Q260197 discusses this
issue and will be available soon.
- Microsoft TechNet Security web site,
Obtaining Support on this Issue
This is a fully supported patch. Information on contacting Microsoft
Technical Support is available at
- June 15, 2000: Bulletin Created.
THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED
"AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL
WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES
WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL,
LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT
CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF
SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF
LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING
LIMITATION MAY NOT APPLY.
Last updated June 15, 2000