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Category:   Application (Generic)  >   Telnet Vendors:   [Multiple Authors/Vendors]
(Conectiva Issues Fix) Telnet Daemons May Give Remote Users Root Level Access Privileges
SecurityTracker Alert ID:  1002256
SecurityTracker URL:  http://securitytracker.com/id/1002256
CVE Reference:   GENERIC-MAP-NOMATCH   (Links to External Site)
Date:  Aug 25 2001
Impact:   Execution of arbitrary code via network, Root access via network, User access via network
Fix Available:  Yes  Vendor Confirmed:  Yes  

Description:   TESO reported that many BSD-derived Telnet daemons (servers) contain a vulnerability that may allow a remote user to obtain root level access on the server.

The vulnerability is reportedly due to a buffer overflow in the telnet option handling.

The following systems are reported to be vulnerable:

BSDI 4.x default, FreeBSD [2345].x default, IRIX 6.5, Linux netkit-telnetd < 0.14, NetBSD 1.x default, OpenBSD 2.x, Solaris 2.x sparc, and "almost any other vendor's telnetd".

A remote user can send a specially formatted option string to the remote telnet server and overwrite sensitive memory, causing arbitrary code to be executed with the privileges of the telnet server (which is typically root level privileges).

Telnet options are reportedly processed by the 'telrcv' function. The results of the parsing, which are to be send back to the client, are stored in the 'netobuf' buffer. It is apparently assumed that the reply data is smaller than the buffer size, so no bounds checking is performed. By using a combination of options, especially the 'AYT' Are You There option, it is possible for a remote user to append data to the buffer. It is reported that the characters that can be written to the buffer are limited, which makes constructing a successful exploit difficult.

The report states that a working exploit has been developed for BSDI, NetBSD and FreeBSD. However, the exploit was not released.

Impact:   A remote user can execute arbitrary code on the server with the privileges of the telnet server, which is typically root level privileges.
Solution:   The vendor has released a fix. See the Source Message for the vendor's advisory containing directions on how to obtain the appropriate fix.
Cause:   Boundary error
Underlying OS:  Linux (Conectiva)
Underlying OS Comments:  many Linux and Unix OSs are vulnerable, but not all - see the Alert text for more information

Message History:   This archive entry is a follow-up to the message listed below.
Jul 18 2001 Telnet Daemons May Give Remote Users Root Level Access Privileges



 Source Message Contents

Subject:  [conectiva-updates] [CLA-2001:413] Conectiva Linux Security Announcement - telnet


-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

- --------------------------------------------------------------------------
CONECTIVA LINUX SECURITY ANNOUNCEMENT 
- --------------------------------------------------------------------------

PACKAGE   : telnet
SUMMARY   : Remote root vulnerability
DATE      : 2001-08-24 15:43:00
ID        : CLA-2001:413
RELEVANT
RELEASES  : 4.0, 4.0es, 4.1, 4.2, 5.0, prg graficos, ecommerce, 5.1, 6.0, 7.0

- -------------------------------------------------------------------------

DESCRIPTION
 The TESO crew reported on Bugtraq a vulnerability affecting the
 telnet server which can be used by remote attackers to obtain root
 privileges. Initially it was thought that the netkit-telnet package,
 used by most linux distributions, was not vulnerable starting with
 version 0.14, but zen-parse showed later on that those versions,
 including the 0.17 one, are also vulnerable.


SOLUTION
 We recommend that all users currently using telnet start using
 openssh instead or some other form of encrypted communication.
 Users who cannot switch to openssh now should upgrade the telnet
 package immediately. Please note that no restart is necessary after
 the upgrade, since telnet is started on demand by inetd.
 
 
 REFERENCES:
 1. http://www.securityfocus.com/bid/3064


DIRECT DOWNLOAD LINKS TO THE UPDATED PACKAGES
ftp://atualizacoes.conectiva.com.br/4.0/SRPMS/telnet-0.17-1U40_1cl.src.rpm
ftp://atualizacoes.conectiva.com.br/4.0/i386/telnet-0.17-1U40_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/4.0es/SRPMS/telnet-0.17-1U40_1cl.src.rpm
ftp://atualizacoes.conectiva.com.br/4.0es/i386/telnet-0.17-1U40_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/4.1/SRPMS/telnet-0.17-1U41_1cl.src.rpm
ftp://atualizacoes.conectiva.com.br/4.1/i386/telnet-0.17-1U41_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/4.2/SRPMS/telnet-0.17-1U42_1cl.src.rpm
ftp://atualizacoes.conectiva.com.br/4.2/i386/telnet-0.17-1U42_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/5.0/SRPMS/telnet-0.17-1U50_1cl.src.rpm
ftp://atualizacoes.conectiva.com.br/5.0/i386/telnet-0.17-1U50_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/5.0/i386/telnet-server-0.17-1U50_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/5.1/SRPMS/telnet-0.17-1U51_1cl.src.rpm
ftp://atualizacoes.conectiva.com.br/5.1/i386/telnet-server-0.17-1U51_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/5.1/i386/telnet-0.17-1U51_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/6.0/SRPMS/telnet-0.17-2U60_1cl.src.rpm
ftp://atualizacoes.conectiva.com.br/6.0/RPMS/telnet-server-0.17-2U60_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/6.0/RPMS/telnet-0.17-2U60_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/7.0/SRPMS/telnet-0.17-2U70_1cl.src.rpm
ftp://atualizacoes.conectiva.com.br/7.0/RPMS/telnet-0.17-2U70_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/7.0/RPMS/telnet-server-0.17-2U70_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/ferramentas/ecommerce/SRPMS/telnet-0.17-1U50_1cl.src.rpm
ftp://atualizacoes.conectiva.com.br/ferramentas/ecommerce/i386/telnet-0.17-1U50_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/ferramentas/ecommerce/i386/telnet-server-0.17-1U50_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/ferramentas/graficas/SRPMS/telnet-0.17-1U50_1cl.src.rpm
ftp://atualizacoes.conectiva.com.br/ferramentas/graficas/i386/telnet-0.17-1U50_1cl.i386.rpm
ftp://atualizacoes.conectiva.com.br/ferramentas/graficas/i386/telnet-server-0.17-1U50_1cl.i386.rpm


ADDITIONAL INSTRUCTIONS
 Users of Conectiva Linux version 6.0 or higher may use apt to perform 
 upgrades of RPM packages:
 - add the following line to /etc/apt/sources.list if it is not there yet
   (you may also use linuxconf to do this):

 rpm [cncbr] ftp://atualizacoes.conectiva.com.br 6.0/conectiva updates

(replace 6.0 with the correct version number if you are not running CL6.0)

 - run:                 apt-get update
 - after that, execute: apt-get upgrade

 Detailed instructions reagarding the use of apt and upgrade examples 
 can be found at http://distro.conectiva.com.br/atualizacoes/#apt?idioma=en


- -------------------------------------------------------------------------
All packages are signed with Conectiva's GPG key. The key and instructions
on how to import it can be found at 
http://distro.conectiva.com.br/seguranca/chave/?idioma=en
Instructions on how to check the signatures of the RPM packages can be
found at http://distro.conectiva.com.br/seguranca/politica/?idioma=en
- -------------------------------------------------------------------------
All our advisories and generic update instructions can be viewed at
http://distro.conectiva.com.br/atualizacoes/?idioma=en

- -------------------------------------------------------------------------
subscribe: conectiva-updates-subscribe@papaleguas.conectiva.com.br
unsubscribe: conectiva-updates-unsubscribe@papaleguas.conectiva.com.br
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Version: GnuPG v1.0.4 (GNU/Linux)
Comment: For info see http://www.gnupg.org

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-----END PGP SIGNATURE-----



 
 


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