Microsoft KB Archive/295090

= Access Violation in W3proxy.exe Because of HTTP VARY Header Processing =

Article ID: 295090

Article Last Modified on 10/26/2007

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APPLIES TO


 * Microsoft Internet Security and Acceleration Server 2000 Standard Edition

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This article was previously published under Q295090



SYMPTOMS
When an outgoing HTTP request is made through Internet Security and Acceleration (ISA) Server, an access violation may occur in W3proxy.exe, causing the Web Proxy service to terminate.



CAUSE
The access violation may occur if the Web browser client's HTTP request contains more than eight HTTP headers in a specific order and the Web server's HTTP response contains a VARY header for some of the HTTP request headers.

Typically, this access violation occurs only if there is a downstream (intermediate) proxy server that is adding HTTP request headers to the Web browser client's request between the Web browser client and ISA Server.



RESOLUTION
A supported hotfix is now available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next service pack that contains this hotfix.

To resolve this problem, submit a request to Microsoft Online Customer Services to obtain the hotfix. To submit an online request to obtain the hotfix, visit the following Microsoft Web site:

http://go.microsoft.com/?linkid=6294451

Note If additional issues occur or any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. To create a separate service request, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

The English version of this fix should have the following file attributes or later:   Date      Time     Version      Size     File name 5/6/2001 02:03PM  3.0.1200.64  373,520  W3proxy.exe



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.



MORE INFORMATION
The HTTP VARY response header is used by a Web server to signal that it has multiple possible responses and, using server-driven negotiation, is returning its best guess as to the proper response. The VARY response header contains field names that are request headers that may be used to select that specific response. The VARY header may have Accept-Language, Accept-Encoding, Accept-Charset, User-Agent, or other fields that define how the page was selected.

Additional query words: crash crashing HF 64 HF64 ISAHF64.exe

Keywords: kbproductlink kbqfe kbhotfixserver kbenv kbprb KB295090

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