CERT Advisory 029

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CERT Advisory

 · 4 years ago

  

 
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CA-91:12                        CERT Advisory 
                               August 22, 1991 
                    Trusted Hosts Configuration Vulnerability 

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The Computer Emergency Response Team/Coordination Center (CERT/CC) has 
received information concerning a vulnerability in the configuration 
of several system files.  This advisory discusses a workaround since 
there are no permanent patches available at this time. 

This vulnerability is present in a very large number of UNIX-based 
operating systems. Therefore, we recommend that ALL sites take the  
corrective actions listed below. 

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I.   DESCRIPTION: 

     The presence of a '-' as the first character in /etc/hosts.equiv, 
     /etc/hosts.lpd and .rhosts files may allow unauthorized access  
     to the system. 
      
II.  IMPACT: 

     Remote users can gain unauthorized root access to the system. 

III. SOLUTION: 
         
     Rearrange the order of entries in the hosts.equiv, hosts.lpd, 
     and .rhosts files so that the first line does not contain  
     a leading '-' character. 

     Remove hosts.equiv, hosts.lpd, and .rhosts files containing only  
     entries beginning with a '-' character. 

     .rhosts files in ALL accounts, including root, bin, sys, news, etc., 
     should be examined and modified as required.  .rhosts files that 
     are not needed should be removed.     

     Please note that the CERT/CC strongly cautions sites about the 
     use of hosts.equiv and .rhosts files.  We suggest that they NOT 
     be used unless absolutely necessary.   

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The CERT/CC wishes to thank Alan Marcum, NeXT Computer, for bringing 
this security vulnerability to our attention.  We would also like to 
thank CIAC for their assistance in testing this vulnerability. 
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If you believe that your system has been compromised, contact CERT/CC via 
telephone or e-mail. 

Computer Emergency Response Team/Coordination Center (CERT/CC) 
Software Engineering Institute 
Carnegie Mellon University 
Pittsburgh, PA 15213-3890 

Internet E-mail: cert@cert.org 
Telephone: 412-268-7090 24-hour hotline: 
           CERT/CC personnel answer 7:30a.m.-6:00p.m. EST, 
           on call for emergencies during other hours. 

Past advisories and other computer security related information are available 
for anonymous ftp from the cert.org (192.88.209.5) system. 

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