Microsoft Knowledge Base Article - Q326830
 

MS02-045: Unchecked Buffer in Network Share Provider May Lead to Denial-of-Service

The information in this article applies to:
  • Microsoft Windows XP Professional
  • Microsoft Windows XP 64-Bit Edition
  • Microsoft Windows 2000 Professional
  • Microsoft Windows 2000 Server
  • Microsoft Windows 2000 Advanced Server
  • Microsoft Windows NT Server 4.0
  • Microsoft Windows NT Server4.0, Terminal Server Edition
  • Microsoft Windows NT Workstation 4.0

SYMPTOMS

Server Message Block (SMB) is the protocol that Microsoft uses to share files, printers, and serial ports. SMB is also used to communicate between computers by using named pipes and mail slots. In a networked environment, servers make file systems and resources available to clients. Clients make SMB requests for resources, and servers make SMB responses in what is described as a client server, request-response protocol.

By sending a specially-crafted packet request, an attacker can mount a denial-of-service attack on the target server computer. This may cause your computer to stop responding (hang). The attacker could use both a user account and anonymous access to accomplish this. Though not confirmed, it may be possible to start arbitrary code.

RESOLUTION

Windows XP

A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that you determine are at risk of attack. Evaluate your computer's physical accessibility, network and Internet connectivity, and other factors to determine the degree of risk to your computer. See the associated Microsoft Security Bulletin to help determine the degree of risk. This fix may receive additional testing. If your computer is sufficiently at risk, Microsoft recommends that you apply this fix now. Otherwise, wait for the next Windows XP service pack that contains this fix.

To resolve this problem immediately, download the fix by following the instructions later in this article or contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone 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.

Download Information

The following file is available for download from the Microsoft Download Center:
Release Date: August 22, 2002

For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:
    Q119591 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 secure servers that prevent any unauthorized changes to the file.

Installation Information

You must restart your computer after you apply this update. This update supports the following Setup switches:
  • -? Display the list of installation switches.
  • -u Unattended mode.
  • -f Force other programs to quit when the computer shuts down.
  • -n Do not back up files for removal.
  • -o Overwrite OEM files without prompting.
  • -z Do not restart when installation is complete.
  • -q Quiet mode (no user interaction).
  • -l List installed hotfixes.
  • -x Extracts the files without running Setup.
For example, the file name -q -z command installs the update without any user intervention, and then does not force the computer to restart.

WARNING: Your computer is vulnerable until you restart it.

File Information

The English version of this fix has the file attributes (or later) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.

The following files are installed to the %WINDIR%\System32 folder.
   Date         Time   Version      Size     File name     Platform
   --------------------------------------------------------------------
   25-Jul-2002  22:15  5.1.2600.50   86,016  Xactsrv.dll   WinXP Pro
   25-Jul-2002  15:27  5.1.2600.50   86,016  Wxactsrv.dll  WinXP 64-bit
   25-Jul-2002  22:15  5.1.2600.50  290,304  Xactsrv.dll   WinXP 64-bit

back to the top

Windows 2000

A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that you determine are at risk of attack. Evaluate your computer's physical accessibility, network and Internet connectivity, and other factors to determine the degree of risk to your computer. See the associated Microsoft Security Bulletin to help determine the degree of risk. This fix may receive additional testing. If your computer is sufficiently at risk, Microsoft recommends that you apply this fix now. Otherwise, wait for the next Windows 2000 service pack that contains this fix.