Knowledge Base

FIX: Http.sys rejects requests that contain separator characters

Article ID: 828726

Article Last Modified on 12/3/2007

APPLIES TO

Microsoft Internet Information Services 6.0

Important This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows Registry

SYMPTOMS

In Microsoft Internet Information Services (IIS) 6.0, when a request contains a header name that includes a question mark (?) character or another separator character, Http.sys rejects the request and sends the following error message to the requestor:

Bad Request (Invalid Header Name).

Additionally, when you use lowercase HTTP verbs like "get," Http.sys rejects the request and sends the following error message to the requestor:

"Bad Request (Invalid Verb)".

CAUSE

This problem occurs because HTTP specifications state that HTTP requests that contain separator characters in the header are not valid. The HTTP specifications also state that HTTP verbs are case-sensitive.

RESOLUTION

Hotfix Information

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

Prerequisites

No prerequisites are required.

Restart Requirement

You must restart your computer after you apply this hotfix.

Hotfix Replacement Information

This hotfix does not replace any other hotfixes.

File Information

The English version of this hotfix has the file attributes (or later file attributes) 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   Version            Size     File name
-----------------------------------------------------------
25-Sep-2003  22:35  5.2.3790.89        334,336  Http.sys
25-Sep-2003  23:59  5.2.3790.89         27,648  Httpapi.dll

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

MORE INFORMATION

Warning If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

Because some clients do not strictly follow the HTTP specifications, these restrictions can be relaxed by installing this hotfix and setting the following registry keys.

Permit Separator Characters in HTTP Headers

Follow these steps, and then quit Registry Editor:

Click Start, click Run, type regedit, and then click OK.
Locate and then click the following key in the registry:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\HTTP\Parameters
On the Edit menu, point to New, and then click DWORD.
Type AllowWeakHeaderNameSyntax, and then press ENTER.
On the Edit menu, click Modify.
Type 1, and then click OK.

Note You must restart your computer for this change to take effect.

Permit HTTP Verbs That Are Not Case-Sensitive