DOCUMENT:Q197085  13-JUN-2001  [sna]
TITLE   :Heap Corruptions Cause Access Violations in SNA Server and SnaBa
PRODUCT :Microsoft SNA Server
PROD/VER:WINDOWS:3.0,4.0
OPER/SYS:
KEYWORDS:

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The information in this article applies to:

 - Microsoft SNA Server, versions 3.0, 3.0 SP1, 3.0 SP2, 3.0 SP3, 4.0, 4.0 SP1 
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SYMPTOMS
========

SNA Server and SnaBase services encounter access violations because of a problem
with application heap corruption.

CAUSE
=====

The application heap corruption occurs when a client application sends an
invalid message to the server. The memory block the heap code is processing has
been overwritten with some invalid data. The Windows NT heap code uses these
size fields to traverse up and down the heap lists, if the fields contain
garbage, the result is a trap. SNA Server does not check for any invalid
messages from the TCP/IP transport DLLs receive buffers.

RESOLUTION
==========

SNA Server 3.0
--------------

To resolve this problem, obtain the latest service pack for SNA Server version
3.0. For additional information, please see the following article in the
Microsoft Knowledge Base:

   Q219049 How to Obtain SNA Server Version 3.0 Service Pack 4



SNA Server 4.0
--------------

This problem was corrected in the latest SNA Server version 4.0 U.S. Service
Pack. For information on obtaining this Service Pack, query on the following
word in the Microsoft Knowledge Base (without the spaces):

S E R V P A C K

The RESOLUTION section above states whether this fix is available as a hotfix or
in the latest service pack. For comparison/testing purposes, the original hotfix
is available on http://hotfix with the following file attributes:

File Name     Date       Time
-----------------------------

Snaip.dll 8/26/98 8:32AM

STATUS
======

Microsoft has confirmed this to be a problem in Microsoft SNA Server versions
3.0 and SNA Server version 4.0. This problem was first corrected in SNA Server
3.0 Service Pack 4.

MORE INFORMATION
================

SNA Server now checks the size of all incoming TCP/IP messages. If it's larger
than allowed, SNA Server will disregard the message and close the client
connection. Event ID 631 will be logged in the Windows NT Application event
viewer with the IP Address of the client.

Additional query words:

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Keywords          :  
Technology        : kbAudDeveloper kbSNAServSearch kbSNAServ300 kbSNAServ400 kbSNAServ300SP3 kbSNAServ300SP1 kbSNAServ400SP1 kbSNAServ300SP2
Version           : WINDOWS:3.0,4.0
Issue type        : kbbug
Solution Type     : kbfix

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Copyright Microsoft Corporation 2001.