exploit the possibilities


Posted Sep 14, 1999

A vulnerability is present in AT&T TCP/IP Release 4.0 running on SVR4 systems for both the 386/486 and 3B2 RISC platforms. The problem is in the remote execution server /usr/etc/rexecd and a new version of rexecd is available from AT&T.

tags | remote, tcp, risc
MD5 | d3ba20fb3622c0b329d3551682a0bfd1


Change Mirror Download

Last Revised: September 19,1997
Attached copyright statement

CERT Advisory
February 25, 1992
AT&T /usr/etc/rexecd Vulnerability

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

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.

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

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.

- ---------------------------------------------------------------------------
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.
- ---------------------------------------------------------------------------

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 (

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

Copyright 1992 Carnegie Mellon University. Conditions for use, disclaimers,
and sponsorship information can be found in
http://www.cert.org/legal_stuff.html and ftp://ftp.cert.org/pub/legal_stuff .
If you do not have FTP or web access, send mail to cert@cert.org with
"copyright" in the subject line.

CERT is registered in the U.S. Patent and Trademark Office.


Revision History:

September 19,1997 Attached Copyright Statement

Version: 2.6.2

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