SCO Unixware Setuid ptrace Local Privilege Escalation Vulnerability

iDefense Security Advisory 02.24.06
http://www.idefense.com/intelligence/vulnerabilities/display.php?id=395
February 24, 2006

I. BACKGROUND

SCO Unixware is a Unix operating system that runs on many OEM platforms.

More information about the product is available from:

  http://www.caldera.com/products/unixware714/

II. DESCRIPTION

Local exploitation of an access validation error in SCO Unixware allows
attackers to gain root privileges.

The vulnerability specifically exists due to a failure to check
permissions on traced executables. The ptrace() system call provides an
interface for debugging other processes on the system. SCO Unixware's
implementation of the ptrace system call fails to check for setuid
permissions on binaries before attaching to the process. This results
in the complete control of memory and execution for the traced process
with root privileges. Attackers can inject data into the running setuid
process and execute arbitrary code with root permissions.

III. ANALYSIS

Exploitation of this vulnerability is trivial. Simply placing shellcode
in the environment and changing the instruction pointer via ptrace() is
enough to elevate privileges.
    
IV. DETECTION

iDefense has confirmed the existence of this vulnerability in SCO
Unixware versions 7.1.3 and 7.1.4. All previous versions of SCO Unixware
are suspected to be vulnerable.

V. WORKAROUND

It is not possible to reduce the impact of this vulnerability other
than to restrict access to the affected systems.

VI. VENDOR RESPONSE

The vendor has released the following advisory to address this issue:

  ftp://ftp.sco.com/pub/updates/UnixWare/SCOSA-2006.9/SCOSA-2006.9.txt

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CAN-2005-2934 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org), which standardizes names for
security problems.

VIII. DISCLOSURE TIMELINE

09/15/2005  Initial vendor notification
10/13/2005  Initial vendor response
02/24/2006  Public disclosure

IX. CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

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X. LEGAL NOTICES

Copyright © 2006 iDefense, Inc.

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Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
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this information.