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CA-92:04 

Last Revised:  September 19,1997

                Attached copyright statement





                               CERT Advisory

                              February 25, 1992

                       AT&T /usr/etc/rexecd Vulnerability 



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The Computer Emergency Response Team/Coordination Center (CERT/CC) has

received information concerning a vulnerability in AT&T TCP/IP Release

4.0 running on SVR4 systems for both the 386/486 and 3B2 RISC platforms.



The existing error, in the remote execution server /usr/etc/rexecd, has

been corrected, and a new executable for rexecd is available from AT&T

by calling 800-543-9935.  Patches may be obtained outside the U.S. by

calling your local technical support.  The numbers associated with the 

fix are 5127 (3.5" media) and 5128 (5.25" media).



The problem does not exist in TCP/IP release 3.2 for SVR3, or any earlier

versions of the TCP/IP product running on either the 3B2 or 386 platforms.



The version of TCP/IP distributed with SVR4 by UNIX(r) System Laboratories,

Inc. (a subsidiary of AT&T) does not contain this vulnerability.



UNIX(r) is a registered trademark of UNIX System Laboratories, Inc.



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I.   Description

     

     A vulnerability has been identified where root privileges may be

     accessed through the use of /usr/etc/rexecd.



II.  Impact



     A user on a remote machine may be able to run commands as root on

     the target host (the host running the affected /usr/etc/rexecd).



III. Solution 

        

     1. Administrators of affected systems should execute, as root, the 

        following command to immediately turn off access to rexecd until

        the new binary can be obtained.



        # chmod 400 /usr/etc/rexecd



     2. Obtain and install the new patch.  The fix will be supplied as

        one diskette, and it comes with one page of instructions documenting

        the procedure to replace the existing /usr/etc/rexecd binary.



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The CERT/CC wishes to thank Bradley E. Smith, Network & Technical Services,

Bradley University, for bringing this vulnerability to our attention and for

providing a corresponding solution.  We would also like to thank AT&T for

their very quick response to this problem.

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If you believe that your system has been compromised, contact CERT/CC or

your representative in FIRST (Forum of Incident Response and Security Teams).



Internet E-mail: cert@cert.org

Telephone: 412-268-7090 (24-hour hotline)

           CERT/CC personnel answer 7:30 a.m.-6:00 p.m. EST(GMT-5)/EDT(GMT-4),

           on call for emergencies during other hours.



Computer Emergency Response Team/Coordination Center (CERT/CC)

Software Engineering Institute

Carnegie Mellon University

Pittsburgh, PA 15213-3890



Past advisories, information about FIRST representatives, and other

information related to computer security are available for anonymous ftp

from cert.org (192.88.209.5).



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Copyright 1992 Carnegie Mellon University. Conditions for use, disclaimers,

and sponsorship information can be found in

http://www.cert.org/legal_stuff.html and http://ftp.cert.org/pub/legal_stuff .

If you do not have FTP or web access, send mail to cert@cert.org with

"copyright" in the subject line.



CERT is registered in the U.S. Patent and Trademark Office.





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Revision History:



September 19,1997  Attached Copyright Statement



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