CIAC: Mime Name Vulnerability in Outlook and Messenger
[These recurring security crises due to buffer overflow errors really
and truly piss me off. In most cases they result from the failure,
largely due to the prevalence of C and the primitive security model of
the major personal computer operating systems, to employ programming
techniques such as automatic bounds-checking that have been well-
understood for forty years. I have taken the liberty of reformatting
this message to 70 columns.]
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[http://www.ciac.org/ciac/bulletins/i-077a.shtml]
INFORMATION BULLETIN
I-077A: Mime Name Vulnerability in Outlook and Messenger
July 28, 1998 00:00 GMT
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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 processed 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 drive.
SOLUTION: Apply patches from Microsoft and Netscape.
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VULNERABILITY Risk is high. While we have not yet heard of anyone
ASSESSMENT: exploiting 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 problem.
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Mime Name Vulnerability in Outlook and Messenger
(Rev. a - Links at Microsoft changed)
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's tags. 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 http://ciac.llnl.gov/ciac/CIACHoaxes.html#goodtimes) 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.
BACKGROUND
==========
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 displayed on 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 and
processed without checking their length. When the length of the header
is longer than one of the buffers in memory where it is stored during
processing, data in the header that falls beyond the end 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.
ASSESSMENT
==========
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.
VULNERABLE APPLICATIONS
=======================
Vulnerabilities in the following applications have been confirmed by
the manufacturers:
Outlook Express v4.72.2106.4 and v4.72.3110.1 (Windows and UNIX)
Outlook '98 (Windows)
Netscape Messenger (Mail) v4.05, or 4.5b1 (Windows)
The current version of Eudora does not appear to be vulnerable. Older
e-mail readers that do not handle mime attachments are not vulnerable.
PATCHES
=======
Information is available from Microsoft at:
http://www.microsoft.com/ie/security/oelong.htm
Patched versions of Outlook and Outlook Express are available from
Microsoft at the URLs:
Outlook 98
Go to: http://support.microsoft.com/support/downloads/LNP499.asp
Download: OUTPATCH.EXE
Outlook Express
First update to Internet Explorer 4.01 at:
http://www.Microsoft.com/ie
Then obtain the patch from:
http://www.microsoft.com/ie/security/oelong.htm
Patches for Macintosh and Solaris versions of Outlook Express will be
available soon at:
http://www.microsoft.com/ie/security/oelong.htm
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:
http://home.netscape.com/download/su1.html
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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.
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For additional information or assistance, please contact CIAC:
Voice: +1 925-422-8193 (8:00 - 18:00 PST, 16:00 - 2:00 GMT)
Emergency (DOE, DOE Contractors, and NIH ONLY):
1-800-759-7243, 8550070 (primary),
8550074 (secondary)
FAX: +1 925-423-8002
STU-III: +1 925-423-2604
E-mail: ciac@llnl.gov
World Wide Web: http://www.ciac.org/
http://ciac.llnl.gov
(same machine -- either one will work)
Anonymous FTP: ftp.ciac.org
ciac.llnl.gov
(same machine -- either one will work)
Modem access: +1 (925) 423-4753 (28.8K baud)
+1 (925) 423-3331 (28.8K baud)
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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
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