FIX: Http.sys rejects requests that contain separator characters

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

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.

Hotfix Information

A supported hotfix is 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 software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if 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. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

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.

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

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

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:

1. Click Start, click Run, type regedit, and then click OK.
2. Locate and then click the following key in the registry:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\HTTP\Parameters
3. On the Edit menu, point to New, and then click DWORD.
4. Type AllowWeakHeaderNameSyntax, and then press ENTER.
5. On the Edit menu, click Modify.
6. 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

Follow these steps, and then quit Registry Editor:

1. Click Start, click Run, type regedit, and then click OK.
2. Locate and then click the following key in the registry:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\HTTP\Parameters
3. On the Edit menu, point to New, and then click DWORD.
4. Type AllowCaseInsensitiveVerbs, and then press ENTER.
5. On the Edit menu, click Modify.
6. Type 1, and then click OK.

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