DOCUMENT:Q179129

TITLE   :STOP 0x0000000A Due to Modified Teardrop Attack

PRODUCT :Microsoft Windows NT

PROD/VER:4.00

OPER/SYS:WINDOWS

KEYWORDS:kbbug4.00 kbbug3.51 kbfix4.00 kbfix3.51 kbfile NTSrvWkst nttcp



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The information in this article applies to:



 - Microsoft Windows NT Workstation versions 3.5 and 3.51

 - Microsoft Windows NT Server versions 3.5 and 3.51

 - Microsoft Windows NT Workstation version 4.0

 - Microsoft Windows NT Server version 4.0

 - Microsoft Windows NT Server Enterprise Edition version 4.0

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SYMPTOMS

========



Windows NT may stop responding (hang) with a STOP 0x0000000A message after

receiving a number of deliberately corrupted UDP packets.



CAUSE

=====



This behavior occurs due to a variation of the "teardrop" attack. Windows

NT 4.0 with Service Pack 3 and the ICMP-fix or Windows NT 3.51 with Service

Pack 5 and the ICMP-fix are not susceptible to the original form of the 

teardrop attack. For more information on the ICMP-fix, please see the 

following article in the Microsoft Knowledge Base:



   ARTICLE-ID: Q154174

   TITLE     : Invalid ICMP Datagram Fragments Hang Windows NT, Windows 95



The modified teardrop attack works by sending pairs of deliberately

constructed IP fragments which are reassembled into an invalid UDP

datagram. Overlapping offsets cause the second packet to overwrite data in

the middle of the UDP header contained in the first packet in such a way

that the datagrams are left incomplete.



As Windows NT receives these invalid datagrams, it allocates kernel memory.

If enough of these invalid datagrams are received Windows NT may hang with

a STOP 0x0000000A.



RESOLUTION

==========



To resolve this problem, obtain the following fix or wait for the next

Windows NT service pack.



Windows NT 4.0:



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)



This hotfix has been posted to the following Internet location:



   ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa/NT40/

   hotfixes-postSP3/teardrop2-fix/



Windows NT 3.51:



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)



This hotfix has been posted to the following Internet location:



   ftp://ftp.microsoft.com/bussys/winnt/winnt-public/fixes/usa/NT351/

   hotfixes-postSP5/teardrop2-fix/



NOTE: This fix supercedes the ICMP-fix, the OOB-fix, and the Land-fix

hotfixes.



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.



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