Original issue date: January 23, 2003
Last revised: January 24, 2003
A complete revision history is at the end of this file.
- Microsoft Windows NT 4.0
- Microsoft Windows NT 4.0, Terminal Server Edition
- Microsoft Windows 2000
- Microsoft Windows XP
A buffer overflow vulnerability in the Microsoft Windows Locator
service could allow a remote attacker to execute arbitrary code or
cause the Windows Locator service to fail. This service is enabled and
running by default on Windows 2000 domain controllers and Windows NT
4.0 domain controllers.
A buffer overflow in the Windows Locator service may make it possible
for a remote attacker to execute arbitrary code on a vulnerable system
by sending an overly large request to the Windows Locator
service. Microsoft describes the Windows Locator service as "a name
service that maps logical names to network-specific names." From
A client that is going to make a Remote Procedure Call
(RPC) can call the Locator service to resolve a logical name for a
network object to a network-specific name for use in the RPC. For
example, if a print server has the logical name "laserprinter", an RPC
client could call the Locator service to find out the network-specific
name that mapped to "laserprinter". The RPC client uses the
network-specific name when it makes the RPC call to the
Further information about this vulnerability can be found in Microsoft
Security Bulletin MS03-001
and in CERT/CC Vulnerability Note VU#610986, which
correspond to CVE candidate CAN-2003-0003.
A remote attacker may be able to execute arbitrary code on a
vulnerable system, or cause the Windows Locator service to fail. An
attacker who is able to compromise a domain controller might be able
to cause the compromised domain controller to trust the attacker's
Apply a patch
Microsoft has provided the following information (contained within MS03-001)
to assist you in downloading the appropriate patch for your
- Windows NT 4.0:
- Windows NT 4.0, Terminal Server Edition:
- Windows 2000:
- Windows XP:
Disable vulnerable service
Until a patch can be applied, you may wish to disable the
Windows Locator service. To determine if the Windows Locator service
is running, Microsoft recommends
To disable the Windows Locator service, Microsoft recommends
- The status of the "Remote Procedure Call (RPC) Locator" service
and how it is started (automatically or manually) can be viewed in the Control
Panel. For Windows 2000 and Windows XP, use Control Panel | Administrative
Tools | Services, and on Windows NT 4.0, use Control Panel | Services.
- It is also possible to determine the status of the Locator service
from the command line by entering: net start
- A list of services will be displayed. If "Remote Procedure Call
(RPC) Locator" appears in the list, then the locator service is running.
- An administrator can disable the Locator service by
setting the RpcLocator service status to "disabled" in the services
- The service can also be stopped via
the command line using the sc.exe program, which ships with Windows
XP and is included as part of the Windows
2000 Resource Kit. The following command will stop the
service: sc stop RpcLocator
- To disable the
service using the command line tool, use the following:
sc config RpcLocator start= disabled
Restrict access to NetBIOS
You may wish to block access to NetBIOS from outside your network
perimeter, specifically by blocking access to ports 139/TCP and
445/TCP. This will limit your exposure to attacks. However, blocking
at the network perimeter would still allow attackers within the
perimeter of your network to exploit the vulnerability. It is
important to understand your network's configuration and service
requirements before deciding what changes are appropriate.
As a best practice, the CERT/CC recommends disabling all services that
are not explicitly required. Before deciding to disable the Windows
Locator service, carefully consider your service requirements.
Please also note that Microsoft is actively deploying the patches for
this vulnerability via Windows Update.
Appendix A. Vendor Information
This appendix contains information provided by vendors. When vendors
report new information, this section is updated and the changes are
noted in the revision history. If a vendor is not listed below, we
have not received their comments.
Please see Microsoft
Security Bulletin MS03-001.
Appendix B. References
This vulnerability was discovered by David Litchfield of Next Generation Security Software
Ltd and was first described in MS03-001.
Author: Ian A. Finlay.
Copyright 2003 Carnegie Mellon University.
January 23, 2003: Initial release
January 24, 2003: Added information about which port nubmers to block