Microsoft KB Archive/842169

= Incoming ARP packets can overwrite static entries in the ARP cache in Windows XP =

Article ID: 842169

Article Last Modified on 10/26/2006

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APPLIES TO


 * Microsoft Windows XP Professional
 * Microsoft Windows XP Home Edition
 * Microsoft Windows XP Professional for Itanium-based systems
 * Microsoft Windows XP Professional for Itanium-based systems

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SYMPTOMS
In Microsoft Windows XP, incoming Address Resolution Protocol (ARP) packets can overwrite static entries in the ARP cache if the sender's protocol address matches an existing static entry that is in the ARP cache. Because an ARP reply that is received without an ARP request can update the ARP cache, a static ARP entry can be spoofed by using a false media access control (MAC) address. Because ARP is unlikely to be routed, this situation may occur only on a local network.



CAUSE
This problem occurs because the ARP client does not distinguish between transient and static cache entries when the ARP client processes incoming ARP packets.



Windows XP service pack information
To resolve this problem, obtain the latest service pack for Microsoft Windows XP. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

322389 How to obtain the latest Windows XP service pack

Windows XP hotfix information
A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it 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 Windows XP service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:

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

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.

Prerequisites
This hotfix requires Windows XP Service Pack 1 (SP1).

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) 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 -- 04-Jun-2004 23:27  5.1.2600.1539  338,048  Tcpip.sys

Windows XP 64-Bit Edition hotfix information
A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it 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 Windows XP service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:

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

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.

Prerequisites
This hotfix requires Windows XP Service Pack 1 (SP1).

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) 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

02-Jun-2004 16:08  5.1.2600.1539  1,106,816   Tcpip.sys



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section. This problem was first corrected in Microsoft Windows XP Service Pack 2.



MORE INFORMATION
For additional information about a fix that resolves this issue in Windows 2000, click the following article number to view the article in the Microsoft Knowledge Base:

842168 Incoming ARP packets can overwrite static entries in the ARP cache in Windows 2000

For additional information about how hotfix packages are named, click the following article number to view the article in the Microsoft Knowledge Base:

816915 New file naming schema for Microsoft Windows software update packages

For additional information about standard terminology that is used to describe Microsoft software updates, 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

Keywords: kbbug kbfix kbqfe kbwinxpsp2fix kbwinxppresp2fix kbhotfixserver KB842169

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