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	      The Computer Incident Advisory Capability
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                          Information Bulletin

       Vulnerability in Silicon Graphics Inc. "IRIX" /usr/sbin/fmt 


August 29, 1991 08:15 PDT 		                   Number B-38

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PROBLEM: Misconfiguration of /usr/sbin/fmt on some SGI platforms
  causes a breakdown of privacy for files in group MAIL.
PLATFORM: Silicon Graphics Inc. IRIX versions prior to 4.0 (including
  all 3.2 and 3.3.X versions).
DAMAGE: A non-privileged user may read mail belonging to any user,
  including root.
SOLUTIONS: Apply patch described below.
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        Critical Facts about Vulnerability in /usr/sbin/fmt

CIAC has learned of a security problem with the text formatting
program /usr/sbin/fmt supplied by Silicon Graphics.  The program will
allow any user to read mail messages or other files owned by group
"mail" on IRIX versions prior to 4.0 (including all 3.2 and 3.3.X
versions).  This problem has been fixed in version 4.0.  CIAC expects
this vulnerability to be widely exploited due to the recent release of
this information on various Internet information services.  We highly
recommend that you apply this patch immediately.

Silicon Graphics has provided the enclosed patch instructions, and
they have been verified on our SGI IRIX System V Release 3.3.1
machine.

To correct this vulnerability, execute the following command as root:

	chmod 755 /usr/sbin/fmt

Optionally, you could also change the owner and group of the file,
however, SGI has informed us that this change is not necessary:

	chown root.sys /usr/sbin/fmt

If system software should ever be reloaded from a 3.2 or 3.3.*
installation tape or from a backup tape created before the patch was
applied, repeat the above procedure immediately after the software has
been reloaded (before enabling logins by normal users).

SGI customers can contact 1-800-800-4SGI for additional assistance.

For additional information or assistance, please contact CIAC:

	David Brown
	(415) 423-9878 or (FTS) 543-9878  before Sept 1, 1991
	(510) 423-9878 or (FTS) 543-9878  after Sept 1, 1991

	FAX:  (415) 423-8002 or (FTS) 543-8002  before Sept 1, 1991
	FAX:  (510) 423-8002 or (FTS) 543-8002  after Sept 1, 1991

        Note: On September 1, 1991, CIAC's area code will change
              to 510.
 
or send e-mail to:

	ciac@llnl.gov

The assistance of Silicon Graphics, CERT/CC, and Chuck Athey of
Lawrence Livermore National Laboratory is gratefully acknowledged.
Neither the United States Government nor the University of California
nor any of their employees, makes any warranty, expressed or implied,
or assumes any legal liability or responsibility for the accuracy,
completeness, or usefulness of any information, 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 nor the University of California, and shall not be used for
advertising or product endorsement purposes.