ISAPI DLLs That Are Built with MFC Static Libraries Are Vulnerable to Denial of Service Attacks

This article was previously published under Q310649
This article has been archived. It is offered "as is" and will no longer be updated.
An Internet Server Application Programming Interface (ISAPI) server extension that is built by using Microsoft Foundation Classes (MFC) in a static library can be vulnerable to Denial of Service (DoS) attacks.
When MFC processes data from the POST method, MFC allocates enough buffer space to hold the data and then decodes the data into an argument list for the default method of the ISAPI server extension. Under heavy load, the MFC ISAPI code produces arguments that are not valid. When the user code tries to process the information, an access violation occurs.
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 are experiencing this specific problem. This fix may receive additional testing. Therefore, if you are not severely affected by this problem, Microsoft recommends that you wait for the next Microsoft Visual Studio 6.0 service pack that contains this hotfix.

To resolve this problem immediately, 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 typical support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

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.
   Date         Time   Size     File name       -----------------------------------------   19-Sep-2001  16:02  138,948  Eafxis.lib   19-Sep-2001  16:02  749,568  Eafxis.pdb   19-Sep-2001  16:01  102,514  Nafxis.lib   19-Sep-2001  16:01   86,016  Nafxis.pdb				

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.
This vulnerability is only in the Visual C++ MFC static libraries and is not exposed in the MFC dynamic-link libraries (DLLs).

To use this fix, you need a recompile of the affected ISAPI extension with the new files provided in this fix. Copy the updated files in this fix over the existing files. By default, the existing files that have to be updated appear in the following directory:
%Program Files%\Microsoft Visual Studio\VC98\MFC\Lib\

Article ID: 310649 - Last Review: 10/24/2013 08:07:14 - Revision: 2.0

  • Microsoft Visual C++ 6.0 Enterprise Edition
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