Q326322: MS02-037: Rspns to SMTP Client EHLO Cmmd Causes Buffer Overrun
Article: Q326322
Product(s): Microsoft Exchange
Version(s): 5.5,5.5 SP1,5.5 SP2,5.5 SP3,5.5 SP4
Operating System(s):
Keyword(s): kbSecurity kbExchange550preSP5fix KbSECVulnerability KbSECBulletin KbSECHack
Last Modified: 06-AUG-2002
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The information in this article applies to:
- Microsoft Exchange Server, versions 5.5, 5.5 SP1, 5.5 SP2, 5.5 SP3, 5.5 SP4
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SYMPTOMS
========
Exchange Server uses the Internet Mail Service to communicate with other mail
servers by means of Simple Mail Transfer Protocol (SMTP). When the Internet Mail
Service receives an SMTP extended Hello (EHLO) protocol command from a
connecting SMTP server, the Internet Mail Service responds by sending a status
reply that starts with the following line:
250-<Exchange_Server_ID>Hello<connecting_server_ID>
In that line:
- <Exchange_Server_ID> is the fully qualified domain name (FQDN) of the
Exchange Server computer.
- <connecting_server_ID> is either the FQDN of the server that initiated
the connection, or the IP address of the server that initiated the
connection. The FQDN is used if the Exchange Server 5.5 Internet Mail Service
can resolve this information by doing a reverse Domain Name System (DNS)
lookup. The IP address is used if a reverse DNS lookup is not possible or
does not resolve the connecting server's IP address.
A security vulnerability results because of an unchecked buffer in the Internet
Mail Service code that generates the response to the EHLO protocol command. If
the total length of the message exceeds a particular value, the data overruns
the buffer. If the buffer is overrun with random data, the Internet Mail Service
stops responding. However, if the buffer is overrun with carefully chosen data,
an attacker may be able to run code in the security context of the Internet Mail
Service, which runs as the Exchange Server 5.5 service account.
IMPORTANT: Note that the attacker cannot simply send data to the Internet Mail
Service to overrun the buffer. Instead, the attacker has to create a set of
conditions that cause the Internet Mail Service to overrun its own buffer when
it generates the EHLO response. Specifically, the attacker has to ensure that a
reverse DNS lookup not only succeeds, but provides an FQDN with a length that is
sufficient to cause the buffer overrun.
RESOLUTION
==========
A supported fix is now available from Microsoft, but it is only intended to
correct the problem that is described in this article. Apply it only to systems
that you determine are at risk of attack. Evaluate your computer's physical
accessibility, network and Internet connectivity, and other factors to determine
the degree of risk to your computer. See the associated Microsoft Security
Bulletin (http://www.microsoft.com/technet/security/bulletin/ms02-037.asp) to
help determine the degree of risk. This fix may receive additional testing. If
your computer is sufficiently at risk, Microsoft recommends that you apply this
fix now.
To resolve this problem immediately, download the fix by clicking the download
link later in this article or contact Microsoft Product Support Services to
obtain the fix. For a complete list of Microsoft Product Support Services phone
numbers and information about support costs, please visit the following
Microsoft Web site:
http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS
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.
Download Information
--------------------
The following file is available for download from the Microsoft Download Center:
DownloadDownload the Q326322 package now
(http://www.microsoft.com/Downloads/Release.asp?ReleaseID=40666)
Release Date: July 24, 2002
For additional information about how to download Microsoft Support files, click
the following article number to view the article in the Microsoft Knowledge
Base:
Q119591 How to Obtain Microsoft Support Files from Online Services
Microsoft scanned this file for viruses. Microsoft used the most current
virus-detection software that was available on the date that the file was
posted. The file is stored on secure servers that prevent any unauthorized
changes to the file.
Installation Information
------------------------
This update supports the following switches:
- /x Generates a list of the packaged files. You can select the files that you
want to extract and the location.
- /s Performs a silent installation. This switch stops services and installs
the fix with no prompts or user interface (UI). Allow sufficient time for the
fix to be installed, because this switch returns control to the command
prompt well before the installation is finished. Make sure that the fix is
installed. The graphical user interface (GUI) fix package Q<xxxxxx>.exe
should be running in the task manager properties (where <xxxxxx> is the
Microsoft Knowledge Base article Q number and name of the fix).
- /z This switch is the same as the /x switch, but the /z switch automatically
restarts the computer. Do not use the /z switch unless you want to
automatically restart the computer.
- /m Prompts you for the folder locations. You can select the folder locations
of the Microsoft Windows folder, the System folder, the System32 folder, the
Temp folder, the Source folder (which is usually the Temp folder), the System
Windows folder, and the Language folder.
For example, the following command line installs the update without any user
intervention and then does not force the computer to restart:
Q326322enui386 /s
File Information:
The English version of this fix 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 and path
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12-JUL-2002 12:58 5.5.2656.59 209,680 %EXSRVROOT%\Bin\Imcmsg.dll
12-JUL-2002 12:59 5.5.2656.59 503,568 %EXSRVROOT%\Bin\Msexcimc.exe
NOTE: Because of file dependencies, this update may contain additional files.
This update requires Exchange Server 5.5 Service Pack 4.
STATUS
======
Microsoft has confirmed that this problem may cause a degree of security
vulnerability in the Microsoft products that are listed at the beginning of this
article.
MORE INFORMATION
================
For additional information about this vulnerability, visit the following
Microsoft Web site:
http://www.microsoft.com/technet/security/bulletin/ms02-037.asp
Additional query words: security_patch
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Keywords : kbSecurity kbExchange550preSP5fix KbSECVulnerability KbSECBulletin KbSECHack
Technology : kbExchangeSearch kbExchange550 kbZNotKeyword2 kbExchange550SP1 kbExchange550SP2 kbExchange550SP3 kbExchange550SP4
Version : :5.5,5.5 SP1,5.5 SP2,5.5 SP3,5.5 SP4
Issue type : kbbug
Solution Type : kbfix
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