SYMPTOMS
Computers can use the Universal Plug and Play (UPnP)
service to discover and use network-based devices. Windows Millennium Edition
(Me) and Microsoft Windows XP include UPnP services, but Microsoft Windows 98
and Microsoft Windows 98 Second Edition do not. However, the UPnP service can
be installed on a Windows 98-based or Windows 98 Second Edition-based computer
by installing the Internet Connection Sharing (ICS) client that is included
with Windows XP.
This article describes two vulnerabilities that
affect the implementation of UPnP in various products. Although the
vulnerabilities are unrelated, both involve how UPnP-capable computers process
the discovery of new devices on the network.
The first vulnerability
is a buffer-overrun vulnerability. There is an unchecked buffer in one of the
Windows XP components that process NOTIFY directives (messages that advertise
the availability of UPnP-capable devices on the network). By sending a
specially-malformed NOTIFY directive, it would be possible for an attacker to
cause code to run in the context of the UPnP service, which runs with system
privileges on Windows XP. On Windows 98 and Windows Me, there are no security
contexts, and all code runs as part of the operating system. This would enable
the attacker to gain complete control over the computer.
The second
vulnerability occurs because the UPnP service does not sufficiently limit the
steps to which the UPnP service will go to obtain information about using a
newly-discovered device. In the NOTIFY directive that a new UPnP device sends
is information that tells interested computers where to obtain its device
description, which lists the services the device offers, and provides
instructions for using them. By design, the device description may reside on a
third-party server rather than on the device itself. However, the UPnP
implementations do not adequately regulate how it performs this operation, and
this gives rise to two different denial-of-service scenarios.
In the
first denial-of-service scenario, the attacker could send a NOTIFY directive to
a UPnP-capable computer, specifying that the device description should be
downloaded from a particular port on a particular server. If the server was
configured to simply echo the download requests back to the UPnP service (such
as, by having the Echo service running on the port that the computer was
directed to), the computer could be made to enter an endless download cycle
that could consume some or all of the system's availability. An attacker could
craft and send this directive to a victim's computer directly, by using the
computer's IP address. Or, the attacker could send this same directive to a
broadcast and multicast domain and attack all Windows XP-based computers in
that broadcast or multicast domain, consuming some or all of those system's
availability.
In the second denial-of-service scenario, an attacker
could specify a third-party server as the host for the device description in
the NOTIFY directive. If enough computers responded to the directive, it could
have the effect of flooding the third-party server with invalid requests, in a
distributed denial-of-service attack. As with the first denial-of-service
scenario, an attacker could either send the directives to the victim directly,
or to a broadcast or multicast domain.
Mitigating Factors
General
Standard firewall practices (specifically, blocking ports 1900
and 5000) could be used to protect corporate networks from Internet-based
attacks.
Windows 98 and Windows 98 Second Edition
- There is no built-in UPnP support for these operating
systems. Windows 98-based or Windows 98 Second Edition-based computers would
only be affected if the ICS client from Windows XP had been installed on the
computer.
- Windows 98-based or Windows 98 Second Edition-based
computers that have installed the ICS client from a Windows XP-based computer
that has already applied this patch are not vulnerable.
Windows Me
Windows Me provides built-in UPnP support, but by default, it is
not installed or running. However, some OEMs configure computers so that the
UPnP service is installed and running.
Windows XP
Internet Connection Firewall (ICF), which runs by default, would
impede an attacker's ability to mount a successful directed attack. However,
because the ICF does not block incoming broadcast or multicast traffic, it
would not protect against those attacks.
RESOLUTION
A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that this article describes. Apply it only to systems that you determine are at risk of attack. Evaluate the computer's physical accessibility, network and Internet connectivity, and other factors to determine the degree of risk to the computer. See the associated
Microsoft Security Bulletin to help determine the degree of risk. This hotfix may receive additional testing. If the computer is sufficiently at risk, we recommend that you apply this hotfix now.
To resolve this problem immediately, download the hotfix by following the instructions later in this article or contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:
Note In special cases, charges that are ordinarily incurred for support calls may be canceled, if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question. The following file is available for
download from the Microsoft Download Center:
Release Date: December 20, 2001
For additional
information about how to download Microsoft Support files, click the following
article number to view the article in the Microsoft Knowledge Base:
119591 How to Obtain Microsoft Support Files from Online Services
Microsoft scanned this file for viruses. Microsoft used the most
current virus-detection software that was available on the date that the file
was posted. The file is stored on security-enhanced servers that help to
prevent any unauthorized changes to the file.
The English version of this fix should have the
following file attributes or later:
Date Time Version Size File name
------------------------------------------------------
13-Dec-2001 18:15 2,525 314757up.inf
11-Dec-1997 05:33 4.72.2811.0 80,864 Advpack.dll
27-Jul-1998 14:48 4.10.0.1998 36,864 Qfecheck.exe
09-Feb-1996 17:28 8,042 Qfecheck.hlp
13-Dec-2001 18:15 886 Qfereg.inf
13-Dec-2001 17:37 4.90.3003.0 39,184 Ssdpapi.dll
13-Dec-2001 17:38 4.90.3003.0 57,104 Ssdpsrv.exe
13-Dec-2001 17:39 4.90.3003.0 133,904 Upnp.dll
04-Dec-1997 12:02 4.71.704.0 2,272 W95inf16.dll
04-Dec-1997 12:02 4.71.16.0 4,608 W95inf32.dll
