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__________________________________________________________
The U.S. Department of Energy
Computer Incident Advisory Capability
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INFORMATION BULLETIN
Microsoft Exchange Denial of Service Attacks
August 5, 1998 22:00 GMT Number I-080
______________________________________________________________________________
PROBLEM: Vulnerabilites have been identified in the Exchange Internet
Mail Service (IMS), the service that handles the SMTP protocol,
and the Information Store, the service that handles the NNTP
protocol
PLATFORM: Microsoft Exchange Server 5.0 and 5.5.
DAMAGE: If exploited, an attacker may be able to cause a Denial of
Service.
SOLUTION: Apply hotfixes. If you cannot apply the hotfix immediately,
Microsoft recommends that you configure the Server Monitor in
Microsoft Exchange Server Administrator to automatically
restart the affected services if they stop.
______________________________________________________________________________
VULNERABILITY An attacker can disrupt an organization by crashing a Microsoft
ASSESSMENT: Exchange Server over the network. This attack will stop e-mail
and other services that Exchange provides for the organization.
______________________________________________________________________________
[ Start ISS Security Advisory ]
======================
ISS Security Advisory
July 24, 1998
Denial of Service attacks against Microsoft Exchange 5.0 to 5.5
Synopsis:
An attacker can disrupt an organization by crashing Microsoft Exchange
Server over the network. This attack will stop e-mail and other services
that Exchange provides for the organization.
Recommended Action:
Install vendor supplied hotfixes for Microsoft Exchange 5.0, and 5.5.
Hotfixes are available for Exchange 5.0 and 5.5 at the following locations:
Exchange Server 5.0 ALL LANGUAGES:
ftp://ftp.microsoft.com/bussys/exchange/exchange-public/fixes/
Eng/Exchg5.0/Post-SP2-STORE/
ftp://ftp.microsoft.com/bussys/exchange/exchange-public/fixes/
Eng/Exchg5.0/Post-SP2-IMS/
Exchange Server 5.5 ENGLISH:
ftp://ftp.microsoft.com/bussys/exchange/exchange-public/fixes/
Eng/Exchg5.5/PostRTM/STORE-FIX
ftp://ftp.microsoft.com/bussys/exchange/exchange-public/fixes/
Eng/Exchg5.5/PostRTM/IMS-FIX
Exchange Server 5.5 FRENCH:
ftp://ftp.microsoft.com/bussys/exchange/exchange-public/fixes/
Frn/Exchg5.5/PostRTM/STORE-FIX
ftp://ftp.microsoft.com/bussys/exchange/exchange-public/fixes/
Frn/Exchg5.5/PostRTM/IMS-FIX
Exchange Server 5.5 GERMAN:
ftp://ftp.microsoft.com/bussys/exchange/exchange-public/fixes/
Ger/Exchg5.5/PostRTM/STORE-FIX
ftp://ftp.microsoft.com/bussys/exchange/exchange-public/fixes/
Ger/Exchg5.5/PostRTM/IMS-FIX
Exchange Server 5.5 JAPANESE:
ftp://ftp.microsoft.com/bussys/exchange/exchange-public/fixes/
Jpn/Exchg5.5/PostRTM/STORE-FIX
ftp://ftp.microsoft.com/bussys/exchange/exchange-public/fixes/
Jpn/Exchg5.5/PostRTM/IMS-FIX
If you cannot apply the hotfix immediately, Microsoft recommends that you
configure the Server Monitor in Microsoft Exchange Server Administrator to
automatically restart the affected services if they stop.
Determining if you are vulnerable:
If you are running Microsoft Exchange 5.0 or 5.5 without appropriate
hotfixes, you are vulnerable to the attacks.
Description:
There are vulnerabilities in the Exchange Internet Mail Service (IMS), the
service that handles the SMTP protocol, and the Information Store, the
service that handles the NNTP protocol, that will allow an attacker to
crash the Internet Mail Service or the Information Store. These
vulnerabilities are related to the way that the IMS handles the AUTH
command and how the Information Store's NNTP server handles AUTHINFO. Both
of these systems experience buffer overflow issues.
A similar problem not related to the buffer overflow issue involves how IMS
handles the AUTH command. This issue will also cause the service to crash.
Note that when the Internet Mail Service crashes, the rest of Microsoft
Exchange will still operate. When the Information Store crashes, Exchange
Server cannot operate.
Vulnerable Versions:
Microsoft Exchange Server 5.0 and 5.5 are vulnerable without hotfixes
applied
Additional Information:
There are two Microsoft Knowledge Base articles that address these issues
- -- Q188369 and Q188341. These can be obtained from Microsoft Support Online
at http://support.microsoft.com. ISS X-Force thanks the Microsoft Exchange
group for providing assistance and patches to these issues in a timely
fashion.
These security issues were discovered by Jon Larimer of ISS X-Force
<jlarimer@iss.net>.
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Copyright (c) 1998 by Internet Security Systems, Inc.
Permission is hereby granted for the redistribution of this Alert
electronically. It is not to be edited in any way without express consent
of X-Force. If you wish to reprint the whole or any part of this Alert in
any other medium excluding electronic medium, please e-mail xforce@iss.net
for permission.
Disclaimer
The information within this paper may change without notice. Use of this
information constitutes acceptance for use in an AS IS condition. There are
NO warranties with regard to this information. In no event shall the author
be liable for any damages whatsoever arising out of or in connection with
the use or spread of this information. Any use of this information is at
the user's own risk.
X-Force PGP Key available at: http://www.iss.net/xforce/sensitive.html as
well as on MIT's PGP key server and PGP.com's key server.
X-Force Vulnerability and Threat Database: http://www.iss.net/xforce
Please send suggestions, updates, and comments to:
X-Force <xforce@iss.net> of Internet Security Systems, Inc.
- --------------
[ End ISS Security Advisory ]
______________________________________________________________________________
CIAC wishes to acknowledge the contributions of Internet Security Systems,
Inc. for the information contained in this bulletin.
______________________________________________________________________________
CIAC, the Computer Incident Advisory Capability, is the computer
security incident response team for the U.S. Department of Energy
(DOE) and the emergency backup response team for the National
Institutes of Health (NIH). CIAC is located at the Lawrence Livermore
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I-077: Mime Name Vulnerability in Outlook and Messenger
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