DEC Ultrix Vulnerability

Original issue date: May 1, 1991
Last revised: September 18, 1997
Attached copyright statement

A complete revision history is at the end of this file.

The Computer Emergency Response Team/Coordination Center (CERT/CC) has received information concerning a vulnerability in Digital Equipment Corporation's (DEC) Ultrix operating system versions 4.0 and 4.1 for all DEC architectures.  The vulnerability has been fixed in version 4.2 which will be shipped beginning in late May.  DEC has also provided a suggested fix for versions 4.0 and 4.1.

I. Description

By default, /usr/bin/chroot is improperly installed in Ultrix versions 4.0 and 4.1.  

II. Impact

System users can gain unauthorized privileges.

III. Solution

Change the permission on the file /usr/bin/chroot.
# chmod 700 /usr/bin/chroot   

Our thanks to Eric R. Jorgensen and Brian Ellis of UnixOps / Distributed Computing Services at the University of Colorado, Boulder, for bringing this problem to our attention.  The CERT/CC would also like to thank Digital for their response to this vulnerability.

This document is available from:

CERT/CC Contact Information

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

CERT/CC 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 hours, on U.S. holidays, and on weekends.

Using encryption

We strongly urge you to encrypt sensitive information sent by email.  Our public PGP key is available from

If you prefer to use DES, please call the CERT hotline for more information.

Getting security information

CERT publications and other security information are available from our web site

* "CERT" and "CERT Coordination Center" are registered in the U.S. Patent and Trademark Office.

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Copyright 1991 Carnegie Mellon University.

Revision History
September 18,1997  Attached Copyright Statement