FIX: IIS 6.0 may close a connection unexpectedly when a client application sends approximately 4,000 POST requests by using chunked transfer encoding on the same HTTP connection

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Consider the following scenario:
  • A client application sends approximately 4,000 POST requests to a server that is running Internet Information Services (IIS) 6.0.
  • The client application sends the POST requests by using chunked transfer encoding on the same HTTP connection.
  • The HTTP Keep-Alives feature is enabled on the server that is running IIS 6.0.
In this scenario, IIS 6.0 may close the connection unexpectedly by sending TCP RESET packets to the client application. Additionally, you may see a Timer_HeaderWait error in the HTTPERR#.log file. The log entry may resemble the following:
#Date: <Date> <Time>#Fields: date time c-ip c-port s-ip s-port cs-version cs-method cs-uri sc-status s-siteid s-reason s-queuename<Date> <Time> <Client IP> <Client Port> <Server IP> <Server Port> - - - - - Timer_HeaderWait
Note The HTTPERR#.log file is used for HTTP.sys error logging. By default, this file is located in the following directory:
This issue occurs because of a code defect in the HTTP kernel-mode driver (HTTP.sys) that occurs when the HTTP kernel-mode driver parses the POST requests that are sent by using chunked transfer encoding.

Hotfix information

A supported hotfix is now available from Microsoft. However, it is intended to correct only the problem that is described in this article. Apply it only to systems that are experiencing this specific problem. This hotfix may 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 immediately, contact Microsoft Customer Support Services to obtain the hotfix. For a complete list of Microsoft Customer Support Services telephone 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 usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.


You must have Windows Server 2003 Service Pack 2 (SP2) installed to apply this hotfix.

Restart requirement

You must restart the 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 item in Control Panel.
File nameFile versionFile sizeDateTimePlatform
File nameFile versionFile sizeDateTimePlatform
File nameFile versionFile sizeDateTimePlatform
To work around this problem if you cannot apply this hotfix, do not use chunked transfer encoding in POST requests from the client application. Instead, use the Content-Length entity-header field.

For more information about the Content-Length entity-header field, see section 14.13 of RFC 2616. To do this, visit the following World Wide Web Consortium (W3C) Web site:Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section. This problem is resolved in IIS 7.0.
More information
For more information about chunked transfer encoding, see section 3.6 of RFC 2616. To do this, visit the following World Wide Web Consortium (W3C) Web site:For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates

Article ID: 967853 - Last Review: 01/15/2015 05:22:00 - Revision: 3.0

Microsoft Internet Information Services 6.0

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