Microsoft Product Support Services   All Products  |   Support  |   Search  | Home
  Support Home  |   Self Support  |   Assisted Support  |   Custom Support  |

Windows 2000 Event Viewer Contains an Unchecked Buffer

The information in this article applies to:
  • Microsoft Windows versions 2000, 2000 SP1 Professional
  • Microsoft Windows versions 2000, 2000 SP1 Server
  • Microsoft Windows versions 2000, 2000 SP1 Advanced Server


The Windows 2000 Event Viewer snap-in has an unchecked buffer in a section of the code that displays the detailed view of event records. If Event Viewer attempts to display an event record that contains specially malformed data in one of the fields, either of two outcomes can occur. In the less serious case, Event Viewer could stop working. In the more serious case, code of a malicious user's choice could be made to run by using a buffer overrun.

By design, unprivileged processes can log events in the System and Application logs, and interactively logged-on, unprivileged users can view them. However, only privileged processes can log events in the Security log, and only interactively logged-on administrators can view them. If the vulnerability were exploited to run code of a malicious user's choice, the code would run in the security context of the user who viewed the affected record.

Mitigating Factors

  • Simply perusing the listing of events in a log would not allow the vulnerability to be exploited. It could only be exploited if the user opened an affected record to view the event details.

  • Although Event Viewer might be considered to be an administrative tool, there is no guarantee that the user who opens a particular event record would be privileged. Unprivileged users can read the System and Application logs. Although the Security log can be read only by privileged users, only privileged processes can write to it.

  • Microsoft believes that it is not possible to manipulate the typical auditing functions of any Windows 2000 service to create an event record that would exploit this vulnerability. Instead, custom code would need to be created and run to create such a record.

  • If you are using a firewall and are taking other appropriate precautions, only authenticated users have access to network computers and can write event log records.


A supported fix is now available from Microsoft, but it is only intended to correct the problem described in this article and should be applied only to systems that are determined to be at risk of attack. Please evaluate your computer's physical accessibility, network and Internet connectivity, and other factors to determine the degree of risk to your computer. Please see the associated Microsoft Security Bulletin to help make this determination. This fix may receive additional testing at a later time, to further ensure product quality. 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.

To resolve this problem immediately, download the fix as instructed below or contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information on support costs, please go to the following address on the World Wide Web:
NOTE: In special cases, charges that are normally incurred for support calls may be canceled, if a Microsoft Support Professional determines that a specific update will resolve your problem. Normal 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:
[GRAPHIC: Download]Download Q285156_w2k_sp3_x86_en.exe now
For additional information about how to download Microsoft Support files, click the article number below to view the article in the Microsoft Knowledge Base:
Q119591 How to Obtain Microsoft Support Files from Online Services
Microsoft used the most current virus detection software available on the date of posting to scan this file for viruses. Once posted, the file is housed on secure servers that 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
   02/14/2001  03:57p  5.0.2195.3256  157,456  Els.dll 


Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article.


For more information on this vulnerability, please see the following Microsoft Web site:
For additional information about how to install Windows 2000 and Windows 2000 hotfixes at the same time, click the article number below to view the article in the Microsoft Knowledge Base:
Q249149 Installing Microsoft Windows 2000 and Windows 2000 Hotfixes

Additional query words: security_patch Patch Available for Malformed Event Record Vulnerability

Keywords : kbWin2000PreSP3Fix
Issue type : kbbug
Technology : kbwin2000AdvServ kbwin2000AdvServSearch kbwin2000S kbwin2000Ssearch kbwin2000Search kbwin2000ProSearch kbwin2000Pro

Last Reviewed: February 28, 2001
© 2001 Microsoft Corporation. All rights reserved. Terms of Use.

Article ID: Q285156

Last Reviewed:
February 28, 2001

Send to a friend

Provided by
Microsoft Product Support Services

Did the information in this article help answer your question?

Did not apply

Please provide additional comments about this information.
(255 character max)