NGSSoftware Insight Security Research Advisory

Name: Locator Service Buffer Overflow Vulnerability
Systems Affected: Windows 2000/XP/NT
Severity: High Risk / Critical
Category: Buffer Overrun
Vendor URL: http://www.microsoft.com/
Author: David Litchfield (david@ngssoftware.com)
Date: 29th January 2003
Advisory number: #NISR29012003
Tool: http://www.ngssoftware.com/rpclocator.html

Description
***********
There is a remotely exploitable buffer overflow vulnerability in the
Microsoft RPC (Remote Procedure Call) Locator Service on Windows platforms.
The RPC Locator Service maintains a list of RPC services and servers on the
network. Typically only domain controllers run the Locator service by
default and these machines are the most at risk.

Details
*******
When searching for RPC Services on the network a Windows RPC client will
connect to the domain controller over TCP port 139/445 (the SMB ports) and
search for services/servers through the "locator" named pipe. An attacker
can overflow a stack based buffer in the Locator service process by
searching for an overly long string for an entry name to use in looking for
binding handles. This problem arises due to an unsafe call to wcscpy().

Fix Information
***************
NGSSoftware advised Microsoft to this problem at the end of October of 2002.
Microsoft released the patch to resolve this issue last week.

http://www.microsoft.com/security/security_bulletins/ms03-001.asp

NGSSoftware have written a free command line scanner to locate Microsoft
computers running the RPC Locator service on the network. This may be
downloaded from the NGSSite. [Please note that this scanner does not test
for the actual vulnerability, but rather helps locate those machines most at
risk. Although sample exploit code has been provided to the vendor, due to
the recent events of last weekend, NGSSoftware are loathe to publish this
publicly at this juncture - however we may after a grace period.]

http://www.ngssoftware/rpclocator.html

A check for this issue is already in Typhon, NGSSoftware's advanced
vulnerability assessment scanner, of which more information is available
from the NGSSite, http://www.ngssoftware.com.

Further Information
*******************
For further information about the scope and effects of buffer overflows,
please see

http://www.ngssoftware.com/papers/non-stack-bo-windows.pdf
http://www.ngssoftware.com/papers/ntbufferoverflow.html
http://www.ngssoftware.com/papers/bufferoverflowpaper.rtf
http://www.ngssoftware.com/papers/unicodebo.pdf

About NGSSoftware
*****************
NGSSoftware design, research and develop intelligent, advanced application
security assessment scanners. Based in the United Kingdom, NGSSoftware have
offices in the South of London and the East Coast of Scotland. NGSSoftware's
sister company NGSConsulting, offers best of breed security consulting
services, specialising in application, host and network security
assessments.

http://www.ngssoftware.com/
http://www.ngsconsulting.com/

Telephone +44 208 401 0070
Fax +44 208 401 0076

enquiries@ngssoftware.com