CERT Advisory 040

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CERT Advisory

 · 4 years ago

  

 
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CA-92:04                        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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