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TUCoPS :: Windows Net Apps :: ciaci077.txt

Windows MIME Name Vulnerability Outlook Messenger


                       The U.S. Department of Energy
                    Computer Incident Advisory Capability
                           ___  __ __    _     ___
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                             ADVISORY BULLETIN

                Mime Name Vulnerability in Outlook and Messenger

Updated Aug 11, 1998 20:00 GMT                                   Number I-077A
PROBLEM:       A buffer overflow vulnerability has been identified in
               Microsoft Outlook, Outlook Express, and Netscape Messenger  
               (Mail) that allows an e-mail or news message to contain
               malicious code in a mime header. That code is executed when the
               header is read by the e-mail/news reader. All of these
               e-mail/news readers are widely distributed with popular 
               packages such as Internet Explorer, Windows 98, Windows 97,
               Office 97, and Netscape Communicator.
PLATFORM:      Any platform that runs the vulnerable e-mail/news readers:
               Windows 95, Windows 98, Windows NT, Macintosh and Solaris.
DAMAGE:        If exploited, this vulnerability allows a remote user to run
               arbitrary code on a users machine with the user's privileges.
               The remotely executed code could do anything from sending
               thousands of e-mails in the user's name to formatting the hard
SOLUTION:      Apply patches from Microsoft and Netscape.
VULNERABILITY  Risk is high. While we have not yet heard of anyone exploiting
ASSESSMENT:    this vulnerability for malicious purposes, the ease with which
               it can be exploited, the wide distribution of vulnerable
               readers, and the potential for damage makes it a very serious

Mime Name Vulnerability in Outlook and Messenger

CIAC has received information about a vulnerability in the Microsoft and
Netscape e-mail/news products: Outlook, Outlook Express, and Messenger (Mail).
These e-mail/news programs improperly handle the mime name tags used to
identify attachments to e-mail/news messages. An improper name tag can result
in a buffer overflow condition when the program processes the attachment. As
the reader generally processes the attachments when the user reads the
message, the buffer overflow condition can be initiated, by simply reading the
e-mail/news message.

The buffer overflow condition can then be exploited to run any arbitrary code
contained in the attachment. The code runs with the user's permissions to do
anything the user can do such as re-send the e-mail to the users mailing list,
change files, or format the hard drive.

While at first glance this appears to the Good_Times hoax come to life (see this is not really the
case. Good_Times was supposed to run itself on any system that downloaded and
read the Good_Times message. This mime name vulnerability is caused by
improperly handled mime headers in a few versions of some very popular e-
mail/news readers. By replacing the vulnerable readers with properly patched
versions, this vulnerability is eliminated.


The Multipurpose Internet Mail Extensions or MIME is a protocol for sending
non-ASCII text or multi-part documents as part of e-mail or news message.
Users of the readers rarely see the mime headers since they are stripped out
of the message as it is downloaded onto the user's machine. The mime headers
tell the reader where the different parts of the message begin and end, what
type of data is contained in the message part, what encoding is used to
convert the message, what the name of the file is that was attached as a
message part, and other information necessary for the successful transmission
of the data.

In the vulnerable readers, the headers are read into memory without checking
their length. When the length of the header is longer than the buffer in
memory where the reader tries to store it, data in the header beyond the
length of the buffer overwrites other code and data in memory. This
overwriting is the classic "buffer overflow" condition. If the overwritten
piece of memory is part of the running program, the code from the header in
the overwritten part is executed in place of the program's code.


As of the release date of this advisory, we have not heard of anyone
exploiting this vulnerability but we believe it to be extremely serious. Users
should take immediate action to patch vulnerable systems. We base this
assessment on the ease with which the vulnerability can be exploited, the
widespread use of the vulnerable e-mail/news readers, and the potential for
doing serious damage to a computer.

An additional, serious, long-term problem is the fact that these e-mail/news
readers are automatically installed on many systems along with web browsers,
office applications and operating systems. For example, Windows 98 comes
preinstalled on many new systems and contains one of the vulnerable readers.
As the installations are usually done from a CD-ROM, reinstalling a system in
the future for any reason reinstalls the vulnerable readers. Users must insure
that if they reinstall systems that they then replace the vulnerable readers
with appropriately patched versions.


Vulnerabilities in the following applications have been confirmed by the
  Outlook Express v4.72.2106.4 and v4.72.3110.1
  Outlook '98
  Netscape Messenger (Mail) v4.05, or 4.5b1
Earlier versions of these applications are also likely to be vulnerable. The
current version of Eudora does not appear to be vulnerable. Older e-mail
readers that do not handle mime attachments are not vulnerable.


Information is available from Microsoft at:

Patched versions of Outlook and Outlook Express are available from Microsoft
at the URL:

Outlook 98
  Go to:
  Download: OUTPATCH.EXE

Outlook Express
  First update to Internet Explorer 4.01 at:

  Then obtain the patch from:

  Patches for Macintosh and Solaris versions of Outlook Express will be
  available soon at:

Version 4.06 of Netscape Communicator is due out around August 7 and will
contain a patched version of the e-mail reader. Patches will be available
through their Smart Update web page:

Further Information

Further information on the buffer overflow problems may be found at the
following URLs:


A special thanks goes to Ari Takanen and Marko Laakso of the University of
Oulu in Finland and Russ Cooper the Owner/Moderator of the NTBugtraq mailing
list for finding and verifying this vulnerability.

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
National Laboratory in Livermore, California. CIAC is also a founding
member of FIRST, the Forum of Incident Response and Security Teams, a
global organization established to foster cooperation and coordination
among computer security teams worldwide.

CIAC services are available to DOE, DOE contractors, and the NIH. CIAC
can be contacted at:
    Voice:    +1 925-422-8193
    FAX:      +1 925-423-8002
    STU-III:  +1 925-423-2604

For emergencies and off-hour assistance, DOE, DOE contractor sites,
and the NIH may contact CIAC 24-hours a day. During off hours (5PM -
8AM PST), call the CIAC voice number 925-422-8193 and leave a message,
or call 800-759-7243 (800-SKY-PAGE) to send a Sky Page. CIAC has two
Sky Page PIN numbers, the primary PIN number, 8550070, is for the CIAC
duty person, and the secondary PIN number, 8550074 is for the CIAC
Project Leader.

Previous CIAC notices, anti-virus software, and other information are
available from the CIAC Computer Security Archive.

   World Wide Web:
                        (or -- they're the same machine)
   Anonymous FTP:
                        (or -- they're the same machine)
   Modem access:        +1 (925) 423-4753 (28.8K baud)
                        +1 (925) 423-3331 (28.8K baud)

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1. CIAC-BULLETIN for Advisories, highest priority - time critical
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   (SPI) software updates, new features, distribution and
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You will receive an acknowledgment email immediately with a confirmation
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If you include the word 'help' in the body of an email to the above address,
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PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing
communities receive CIAC bulletins.  If you are not part of these
communities, please contact your agency's response team to report
incidents. Your agency's team will coordinate with CIAC. The Forum of
Incident Response and Security Teams (FIRST) is a world-wide
organization. A list of FIRST member organizations and their
constituencies can be obtained via WWW at

This document was prepared as an account of work sponsored by an
agency of the United States Government. Neither the United States
Government nor the University of California nor any of their
employees, makes any warranty, express or implied, or assumes any
legal liability or responsibility for the accuracy, completeness, or
usefulness of any information, apparatus, product, or process
disclosed, or represents that its use would not infringe privately
owned rights. Reference herein to any specific commercial products,
process, or service by trade name, trademark, manufacturer, or
otherwise, does not necessarily constitute or imply its endorsement,
recommendation or favoring by the United States Government or the
University of California. The views and opinions of authors expressed
herein do not necessarily state or reflect those of the United States
Government or the University of California, and shall not be used for
advertising or product endorsement purposes.

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I-072: SunOS Solaris Vulnerabilities (libnsl, SUNWadmap)
I-073: multiscan ('mscan') Tool
I-074: Buffer Overflow in Some Implementations of IMAP Servers
I-075: Microsoft Office 98 Security Vulnerability
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