Microsoft KB Archive/935693

= An ISA Server 2006 Web Proxy client receives error code 502 when a user tries to visit certain Web sites =

Article ID: 935693

Article Last Modified on 9/6/2007

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APPLIES TO


 * Microsoft Internet Security and Acceleration Server 2006 Standard Edition
 * Microsoft Internet Security and Acceleration Server 2006 Enterprise Edition

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Important This article contains information about how to modify the registry. Make sure that you back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows registry



SYMPTOMS
Consider the following scenario. A computer is configured as a Microsoft Internet Security and Acceleration (ISA) Server 2006 Web Proxy client. A user on this client computer tries to visit certain Web sites. In this scenario, the user receives the following error page:

The page cannot be displayed

There is a problem with the page you are trying to reach and it cannot be displayed.

Technical Information (for support personnel)

Error Code: 502 Proxy Error.

The HTTP message includes an unsupported header or an unsupported combination of headers. (12156)

Additionally, you experience the following symptoms:  If you perform a network trace of the HTTP traffic, you capture an HTTP header that begins with a space. If you use ISA Server Monitoring to log the HTTP traffic, the following error information is logged:

ERROR:Multi line header - unsupported.





CAUSE
This problem occurs if a Web server response contains an HTTP header that begins with a space or with a TAB character.



RESOLUTION
A hotfix is available for computers that are running ISA Server 2006. To resolve this problem, install the hotfix that is described in the following Microsoft Knowledge Base article:

935882 Description of the ISA Server 2006 hotfix package that is dated April 19, 2007

Hotfix installation information
Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk. By default, this hotfix provides is not automatically enabled. To enable this hotfix, start Registry Editor, and then configure the following registry entry:

Value name: DROP_CONTINUATION_LINES

Value type: REG_DWORD

Value data: 1

You can also configure this registry entry by using a .reg file. To do this, paste the following code into a text file that has a .reg file-name extension. Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\RAT\Stingray\Debug\Web Filters] &quot;DROP_CONTINUATION_LINES&quot;=dword:00000001 After you configure this registry entry, ISA Server 2006 removes any HTTP headers that begin with a space or with a TAB character. Then, ISA Server 2006 forwards the response to the client computer.



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section.



Trace information
When this problem occurs, you may capture trace information that resembles the following:

Http: Response, HTTP/1.1, Status Code = 200 ProtocolVersion: HTTP/1.1 StatusCode: 200, Ok   Reason: OK    Server:  Microsoft-IIS/5.0 Date: : ASP.NET                   < This header begins with a space XPoweredBy: ASP.NET Set-Cookie: SITESERVER=ID=; expires=,  GMT; path=/; domain=.example.com Expires:,  GMT ContentLength: 73313 ContentType: text/html Set-Cookie: ASPSESSIONIDACDSCSDD=LBJHCIECIJKLACBEOEOBMHAC; path=/ Cache-control: private HeaderEnd: CRLF

Keywords: kberrmsg kbfirewall kbtshoot kbfix kbbug kbprb KB935693

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