[Webdev] [Fwd: CERT Advisory CA-2001-21]

Wed Jul 25 10:10:24 IST 2001

-------- Original Message --------
Subject: CERT Advisory CA-2001-21
Date: Tue, 24 Jul 2001 21:50:53 -0400 (EDT)
From: CERT Advisory <cert-advisory at cert.org>
Organization: CERT(R) Coordination Center - +1 412-268-7090
To: cert-advisory at cert.org

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CERT Advisory CA-2001-21 Buffer Overflow in telnetd

   Original release date: July 24, 2001
   Last revised: --
   Source: CERT/CC

   A complete revision history can be found at the end of this file.

Systems Affected

   Systems running versions of telnetd derived from BSD source.

Overview

   The telnetd program is a server for the Telnet remote virtual
terminal
   protocol. There is a remotely exploitable buffer overflow in Telnet
   daemons derived from BSD source code. This vulnerability can crash
the
   server, or be leveraged to gain root access.

I. Description

   There is a remotely exploitable buffer overflow in Telnet daemons
   derived from BSD source code. During the processing of the Telnet
   protocol options, the results of the "telrcv" function are stored in
a
   fixed-size buffer. It is assumed that the results are smaller than
the
   buffer and no bounds checking is performed.

   The vulnerability was discovered by TESO. An exploit for this
   vulnerability has been publicly released; internal testing at CERT/CC
   confirms this exploit works against at least one target system. For
   more information, see

          http://www.team-teso.net/advisories/teso-advisory-011.tar.gz

II. Impact

   An intruder can execute arbitrary code with the privileges of the
   telnetd process, typically root.

III. Solution

Apply a patch

   Appendix A contains information from vendors who have provided
   information for this advisory. We will update the appendix as we
   receive more information. If you do not see your vendor's name, the
   CERT/CC did not hear from that vendor. Please contact your vendor
   directly.

Restrict access to the Telnet service (typically port 23/tcp) using a
firewall or packet-filtering technology.

   Until a patch can be applied, you may wish to block access to the
   Telnet service from outside your network perimeter. This will limit
   your exposure to attacks. However, blocking port 23/tcp at a network
   perimeter would still allow attackers within the perimeter of your
   network to exploit the vulnerability. It is important to understand
   your network's configuration and service requirements before deciding
   what changes are appropriate.

Appendix A. - Vendor Information

   This appendix contains information provided by vendors for this
   advisory. When vendors report new information to the CERT/CC, we
   update this section and note the changes in our revision history. If
a
   particular vendor is not listed below, we have not received their
   comments.

BSDI

   All current versions of BSD/OS are vulnerable. Patches are available
   via our web site at http://www.bsdi.com/services/support/patches and
   via ftp at ftp://ftp.bsdi.com/bsdi/support/patches as soon as testing
   has been completed.

Cisco Systems

   Cisco IOS does not appear to be vulnerable. Certain non-IOS products
   are supplied on other operating system platforms which themselves may
   be vulnerable as described elsewhere in this CERT Advisory. The Cisco
   PSIRT is continuing to investigate the vulnerability to be certain
   and, if necessary, will provide updates to the CERT and publish an
   advisory. Cisco Security Advisories are on-line at
   http://www.cisco.com/go/psirt/.

FreeBSD

   All released versions of FreeBSD are vulnerable to this problem,
which
   was fixed in FreeBSD 4.3-STABLE and FreeBSD 3.5.1-STABLE on July 23,
   2001. An advisory has been released, along with a patch to correct
the
   vulnerability and a binary upgrade package suitable for use on
FreeBSD
   4.3-RELEASE systems. For more information, see the advisory at the
   following location:

ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-01:49.telnetd.asc

   or use an FTP mirror site from the following URL:

http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/mirrors-ftp.html 

Hewlett-Packard

   [This issue is] actively under investigation to determine
   vulnerability ramifications.

Sun Microsystems

   Sun is currently investigating and have confirmed that one can make
   the in.telnetd daemon dump core but Sun has not yet determined if
this
   issue is potentially exploitable on Solaris.

Appendix B. - References

    1. http://www.ietf.org/rfc/rfc0854.txt
    2. http://www.team-teso.net/advisories/teso-advisory-011.tar.gz
    3. http://www.kb.cert.org/vuls/id/745371
    4.
ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-01:49.telnetd.asc
     _________________________________________________________________
     _________________________________________________________________

   The CERT Coordination Center thanks TESO, who published an advisory
on
   this issue. We would also like to thank Jeff Polk for technical
   assistance.
     _________________________________________________________________

   Authors: Jason A. Rafail, Ian A. Finlay, and Shawn V. Hernan.

______________________________________________________________________

   This document is available from:
   http://www.cert.org/advisories/CA-2001-21.html

______________________________________________________________________

CERT/CC Contact Information

   Email: cert at cert.org
          Phone: +1 412-268-7090 (24-hour hotline)
          Fax: +1 412-268-6989
          Postal address:
          CERT Coordination Center
          Software Engineering Institute
          Carnegie Mellon University
          Pittsburgh PA 15213-3890
          U.S.A.

   CERT personnel answer the hotline 08:00-17:00 EST(GMT-5) / EDT(GMT-4)
   Monday through Friday; they are on call for emergencies during other
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Getting security information

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______________________________________________________________________

   NO WARRANTY
   Any material furnished by Carnegie Mellon University and the Software
   Engineering Institute is furnished on an "as is" basis. Carnegie
   Mellon University makes no warranties of any kind, either expressed
or
   implied as to any matter including, but not limited to, warranty of
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     _________________________________________________________________

   Conditions for use, disclaimers, and sponsorship information

   Revision History
July 24, 2001:  Initial release

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