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TUCoPS :: Antique Systems :: 9118.txt

Vulnerability of DEC gateway software

Security Bulletin 9118              DISA Defense Communications System
1 October 1991          Published by: DDN Security Coordination Center
                                  (SCC@NIC.DDN.MIL)   1-(800) 365-3642

                        DEFENSE  DATA  NETWORK
                          SECURITY  BULLETIN

The DDN  SECURITY BULLETIN is distributed  by the  DDN SCC  (Security
Coordination Center) under DISA contract as  a means of  communicating
information on network and host security exposures, fixes, &  concerns
to security & management personnel at DDN facilities.  Back issues may
be  obtained  via  FTP  (or  Kermit)  from  NIC.DDN.MIL  []
using login="anonymous" and password="guest".  The bulletin pathname is
SCC:DDN-SECURITY-yynn (where "yy" is the year the bulletin is issued
and "nn" is a bulletin number, e.g. SCC:DDN-SECURITY-9118).

	Vulnerability of DECnet-Internet gateway software
	in (DEC) ULTRIX versions 4.0, 4.1, and 4.2.

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!                                                                       !
!     The following important  advisory was  issued by the Computer     !
!     Emergency Response Team (CERT)  and is being relayed unedited     !
!     via the Defense Communications Agency's Security Coordination     !
!     Center  distribution  system  as a  means  of  providing  DDN     !
!     subscribers with useful security information.                     !
!                                                                       !
+ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +

CA-91:17                        CERT Advisory
                              September 26, 1991
                      DECnet-Internet Gateway Vulnerability


The Computer Emergency Response Team/Coordination Center (CERT/CC) has
received information concerning a vulnerability in the configuration of
the DECnet-Internet gateway software for Digital Equipment Corporation's 
(DEC) ULTRIX versions 4.0, 4.1, and 4.2 on all Digital architectures.

Digital Equipment Corporation is aware of this problem and a resolution
for this vulnerability will be included in a future release.  Digital
and the CERT/CC strongly recommend that sites exposed to this vulnerability 
immediately institute the workaround detailed in this advisory.


I.   Description

     When installing the DECnet-Internet gateway software it is necessary to
     create a guest account on the ULTRIX gateway host.  By default, this
     account has /bin/csh as its shell.  By virtue of the guest account
     having a valid shell, the DECnet-Internet gateway software can be
     exploited to allow unauthorized root access.

II.  Impact

     Anyone using the DECnet-Internet gateway can gain unauthorized
     root privileges on the ULTRIX gateway host.

III. Solution
     This section describes a workaround for this vulnerability.

     Disable the guest account by editing the /etc/passwd file and setting
     the shell field for the guest account to /bin/false.  Also, ensure the 
     guest account has the string "NoLogin" in the password field as detailed
     in the DECnet-Internet installation manual.  

     Even if you have not installed or are not running the DECnet-
     Internet gateway software, Digital recommends that you implement the
     workaround solution stated above.

The CERT/CC wishes to thank R. Scott Butler of the Du Pont Company for 
bringing this vulnerability to our attention and for his further 
assistance with the temporary workaround.

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

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

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