Invalid ICMP Datagram Fragments Hang Windows NT, Windows 95

• Microsoft Windows NT Workstation version 3.51 and 4.0
• Microsoft Windows NT Server version 3.51 and 4.0
• Microsoft Windows 95

SYMPTOMS

Computers running Windows NT or Windows 95 may stop responding (hang) when they receive corrupted Internet Control Message Protocol (ICMP) datagram fragments from a client.

RESOLUTION

Microsoft has updated the TCP/IP protocol stack to correct this problem. Instructions for installing it are available from Microsoft support channels or directly from the Internet locations below.

NOTE: This hotfix was originally posted on July 7, 1997. A subsequent fix was completed on January 9, 1998 to address another nearly identical attack and this hotfix has replaced the original one. The original hotfix is included in Windows NT 4.0 Service Pack 3. The most recent hotfix is not; however, it is available from the following Internet locations:

Windows NT 4.0

NOTE: Service Pack 3 must be applied to Windows NT 4.0 prior to applying this fix.

This fix should have the following time stamp:

   01/09/98  08:16a               143,664 Tcpip.sys   (Intel)
   01/09/98  08:13a               263,536 Tcpip.sys   (Alpha)

   ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa/NT40/
   hotfixes-postSP3/teardrop2-fix

Windows NT 3.51

NOTE: Service Pack 5 must be applied to Windows NT 3.51 prior to applying this fix.

This fix should have the following time stamp:

   01/14/98  12:04p               123,824 Tcpip.sys   (Intel)
   01/14/98  12:00p               216,848 Tcpip.sys   (Alpha)

   ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa/NT351/
   hotfixes-postSP5/teardrop2-fix

Windows 95

This issue is resolved by the following updated file for Windows 95 and OSR2:

   Vip.386 version 4.0.956 (dated 6/30/97) or later

To install this update, follow these steps:

1. Download the Vipup11.exe file from the Microsoft Software Library to an empty folder.

2. In My Computer or Windows Explorer, double-click the Vipup11.exe file you downloaded in step 1.

3. Follow the instructions on the screen.

 ~ Vipup11.exe (size: 166072 bytes) 

   ARTICLE-ID: Q119591
   TITLE     : How to Obtain Microsoft Support Files from Online Services

   File name  Version    Date/Time        Size     Destination folder
   ----------------------------------------------------------------------
   Vip.386    4.00.956   6/30/97 9:54am   171,672  Windows\System

STATUS

Microsoft has confirmed this to be a problem in Windows NT version 4.0. A supported fix is now available, but has not been fully regression tested and should be applied only to systems experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft recommends that you wait for the next Service Pack that contains this fix. Contact Microsoft Technical Support for more information.

Microsoft has confirmed this to be a problem in Windows NT version 3.51. A supported fix is now available, but has not been fully regression tested and should be applied only to systems experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft recommends that you wait for the next Service Pack that contains this fix. Contact Microsoft Technical Support for more information.

Microsoft has confirmed this to be a problem in Microsoft Windows 95 and OEM Service Release 2 (OSR2). An update to address this problem is now available, but is not fully regression tested and should be applied only to computers experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft does not recommend implementing this update at this time. Contact Microsoft Technical Support for additional information about the availability of this update.