Vulnerability in webdist.cgi

Original issue date: May 6, 1997
Last revised: September 26, 1997
Updated copyright statement

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

The CERT Coordination Center has received reports of a security vulnerability in the webdist.cgi cgi-bin program, part of the IRIX Mindshare Out Box package, available with IRIX 5.x and 6.x. By exploiting this vulnerability, both local and remote users may be able to execute arbitrary commands with the privileges of the httpd daemon. This may be used to compromise the http server and under certain configurations gain privileged access.

Vendor patches are now available from Silicon Graphics Inc. We encourage you to apply patches as soon as possible. For more information, refer to the Silicon Graphics Inc. Security Advisory Number 19970501-02-PX.

The SGI anonymous FTP site is sgigate.sgi.com (204.94.209.1) or its mirror, ftp.sgi.com. Security information and patches can be found in the ~ftp/security and ~ftp/patches directories, respectively.

We will update this advisory as we receive additional information. Please check our advisory files regularly for updates that relate to your site.

Note: Development of this advisory was a joint effort of the CERT Coordination Center and AUSCERT. This material was also released as AUSCERT advisory AA-97.14.


I. Description

A security vulnerability has been reported in the webdist.cgi cgi-bin program available with IRIX 5.x and 6.x. webdist.cgi is part of the IRIX Mindshare Out Box software package, which allows users to install software over a network via a World Wide Web interface.

webdist.cgi allows webdist(1) to be used via an HTML form interface defined in the file webdist.html, which is installed in the default document root directories for both the Netsite and Out Box servers.

Due to insufficient checking of the arguments passed to webdist.cgi, it may be possible to execute arbitrary commands with the privileges of the httpd daemon. This is done via the webdist program.

When installed, webdist.cgi is accessible by anyone who can connect to the httpd daemon. Because of this, the vulnerability may be exploited by remote users as well as local users. Even if a site's webserver is behind a firewall, it may still be vulnerable.

Determining if your site is vulnerable

All sites are encouraged to check their systems for the IRIX Mindshare Out Box software package, and in particular the Webdist Software package which is a subsystem of the Mindshare Out Box software package. To determine if this package is installed, use the command:

# versions outbox.sw.webdist

I = Installed, R = Removed

Name Date Description
I outbox 11/06/96 Outbox Environment, 1.2
I outbox.sw 11/06/96 Outbox End-User Software, 1.2
I outbox.sw.webdist 11/06/96 Web Software Distribution Tools, 1.2

II. Impact

Local and remote users may be able to execute arbitrary commands on the HTTP server with the privileges of the httpd daemon. This may be used to compromise the http server and under certain configurations gain privileged access.

III. Solution

Vendor patches are available from Silicon Graphics Inc. We encourage you to apply patches as soon as possible. For more information, refer to the Silicon Graphics Inc. Security Advisory Number 19970501-02-PX, which is available from the SGI anonymous FTP site

ftp://sgigate.sgi.com

or its mirror,

ftp://ftp.sgi.com

Security information and patches can be found in the ~ftp/security and ~ftp/patches directories, respectively.

You can also prevent the exploitation of this vulnerability by applying the workaround given in Section III.A or removing the package from your systems (Section III.B).

A. Remove execute permissions

Sites should immediately remove the execute permissions on the webdist.cgi program to prevent its exploitation. By default, webdist.cgi is found in /var/www/cgi-bin/, but sites should check all cgi-bin directories for this program.
# ls -l /var/www/cgi-bin/webdist.cgi
-rwxr-xr-x 1 root sys 4438 Nov 6 12:44 /var/www/cgi-bin/webdist.cgi
# chmod 400 /var/www/cgi-bin/webdist.cgi
# ls -l /var/www/cgi-bin/webdist.cgi
-r-------- 1 root sys 4438 Nov 6 12:44 /var/www/cgi-bin/webdist.cgi
Note that this will prevent all users from using the webdist program from the HTML form interface.

B. Remove outbox.sw.webdist subsystem

If the Webdist software is not required, we recommend that sites remove it completely from their systems. This can be done with the command:

# versions remove outbox.sw.webdist

Sites can check that the package has been removed with the command:

# versions outbox.sw.webdist

IV. Additional Measures

Sites should consider taking this opportunity to examine their entire httpd configuration. In particular, all CGI programs that are not required should be removed, and all those remaining should be examined for possible security vulnerabilities.

It is also important to ensure that all child processes of httpd are running as a non-privileged user. This is often a configurable option. See the documentation for your httpd distribution for more details.

Numerous resources relating to WWW security are available. The following pages may provide a useful starting point. They include links describing general WWW security, secure httpd setup, and secure CGI programming.

The World Wide Web Security FAQ:

http://www-genome.wi.mit.edu/WWW/faqs/www-security-faq.html

NSCA's "Security Concerns on the Web" Page:
http://hoohoo.ncsa.uiuc.edu/security/

The following book contains useful information including sections on secure programming techniques.

Practical Unix & Internet Security, Simson Garfinkel and Gene Spafford, 2nd edition, O'Reilly and Associates, 1996.

Please note that the CERT/CC and AUSCERT do not endorse the URLs that appear above. If you have any problems with these sites, please contact the site administrator.

This advisory is a collaborative effort between AUSCERT and the CERT Coordination Center. This material was also released as AUSCERT advisory AA-97.14.



We thank Yuri Volobuev for reporting this problem. We also thank Martin Nicholls (The University of Queensland) and Ian Farquhar for their assistance in further understanding this problem and its solution.

Copyright 1997 Carnegie Mellon University.


Revision History
Sep. 26, 1997   Updated copyright statement
May 07, 1997    Introduction - Corrected the AUSCERT advisory number.
                Acknowledgments - Corrected the AUSCERT advisory
                number and removed a company name.
August 27, 1997 Introduction and Solution - Added patch information.