SunOS/Solbourne loadmodule and modload Vulnerability

Original issue date: December 15, 1993
Last revised: September 19, 1997
Attached copyright statement

A complete revision history is at the end of this file. This advisory supersedes CA-91.22.

The CERT Coordination Center has received information concerning a vulnerability in /usr/etc/modload and $OPENWINHOME/bin/loadmodule in Sun Microsystems, Inc. SunOS 4.1.1, 4.1.2, 4.1.3, and 4.1.3c and OpenWindows 3.0 on all sun4 and Solbourne Computer, Inc. architectures. The problem does not exist in Solaris 2.x, Solaris x86, and sun3 architectures (OpenWindows 3.0 was not released for the sun3 architecture).

Sun has produced a patch for these vulnerabilities for sun4 architectures. It is available through your local Sun Answer Center as well as through anonymous FTP from the ftp.uu.net system in the /systems/sun/sun-dist directory or from the ftp.eu.net system in the /sun/fixes directory.

Solbourne has announced a workaround that is included below.


I. Description

loadmodule(8) and modload(8) can be exploited to execute a user's program using the effective UID of root.

II. Impact

This vulnerability allows a local user to gain root access.

III. Solution

A. SunOS Solution

Obtain and install the appropriate patches according to the instructions included with the patches.

     Module           Patch ID        Filename
     ----------       ---------       ---------------
     loadmodule       100448-02       100448-02.tar.Z
                  BSD Checksum = 19410 5
                  MD5 Checksum = 0215910cf65e055ed3042070bd961a22
     modload          101200-02       101200-02.tar.Z
                  BSD Checksum = 41677 28
                  MD5 Checksum = 626ab2917204eb6e6eb5f165cca3e908

B. Solbourne Solution

Solbourne systems do not support the "loadmodule" functionality. This vulnerability can be fixed on Solbourne systems by removing the setuid bit:

chmod 0755 /usr/openwin/bin/loadmodule

The modload program does not need to replaced or changed.


The CERT Coordination Center wishes to thank Sun Microsystems, Inc. and Solbourne Computers, Inc. for their support in responding to this problem.

Copyright 1993 Carnegie Mellon University.


Revision History
September 19,1997  Attached Copyright Statement