Internet Security Systems Security Brief
October 14, 2003

Microsoft RPC Race Condition Denial of Service

Synopsis:

ISS X-Force has discovered a flaw in the Microsoft RPC service during a
routine audit that may allow remote attackers to trigger a Denial of
Service (DoS) condition on vulnerable hosts. This vulnerability exists in
the most current patch-levels of the Windows operating systems, including
computers patched against the issues described in Microsoft Security
Bulletin MS03-039. This vulnerability has been reported by various sources
as a new exploit vector against the vulnerability disclosed in MS03-039.
This assessment is incorrect. The vulnerability described in this Advisory
manifests as a result of a separate multi-threaded race condition when
processing incoming RPC requests.

Impact:

X-Force has demonstrated that a DoS vulnerability exists by exploiting the
race condition. Attackers can take advantage of this vulnerability by
crashing the Microsoft RPC service, and/or forcing vulnerable systems to
reboot. X-Force has not demonstrated that this vulnerability can be used
to execute arbitrary code or to compromise a vulnerable system.
Significant  barriers exist which may prevent reliable exploitation
outside of controlled lab conditions.

Affected Versions:

Microsoft Windows 2000
Microsoft Windows XP

For the complete ISS X-Force Security Advisory, please visit:
http://xforce.iss.net/xforce/alerts/id/155

______

About Internet Security Systems (ISS)
Founded in 1994, Internet Security Systems (ISS) (Nasdaq: ISSX) is a
pioneer and world leader in software and services that protect critical
online resources from an ever-changing spectrum of threats and misuse.
Internet Security Systems is headquartered in Atlanta, GA, with
additional operations throughout the Americas, Asia, Australia, Europe
and the Middle East.

Copyright (c) 2003 Internet Security Systems, Inc. All rights reserved
worldwide.

Permission is hereby granted for the electronic redistribution of this
document. It is not to be edited or altered in any way without the
express written consent of the Internet Security Systems X-Force. If you
wish to reprint the whole or any part of this document in any other
medium excluding electronic media, please email xforce@iss.net for
permission.

Disclaimer: The information within this paper may change without notice.
Use of this information constitutes acceptance for use in an AS IS
condition. There are NO warranties, implied or otherwise, with regard to
this information or its use. Any use of this information is at the
user's risk. In no event shall the author/distributor (Internet Security
Systems X-Force) be held liable for any damages whatsoever arising out
of or in connection with the use or spread of this information.
X-Force PGP Key available on MIT's PGP key server and PGP.com's key
server,
as well as at http://www.iss.net/security_center/sensitive.php
Please send suggestions, updates, and comments to: X-Force
xforce@iss.net of Internet Security Systems, Inc.