IBM AIX pioout Arbitrary Library Loading Vulnerability

iDefense Security Advisory 07.26.07
http://labs.idefense.com/intelligence/vulnerabilities/ 
Jul 26, 2007

I. BACKGROUND

The pioout program is a setuid root application, installed by default
under multiple versions of IBM AIX, that is used to interface with the
printer driver. More information can be found at the following URL.

http://publib.boulder.ibm.com/infocenter/pseries/v5r3/topic/com.ibm.aix.cmds/doc/aixcmds4/pioout.htm 

II. DESCRIPTION

Local exploitation of an arbitrary library loading vulnerability in the
'pioout' program, as included with IBM Corp.'s AIX operating system,
allows an attacker to execute arbitrary code with root privileges.

The vulnerability exists due to the application loading an arbitrary
shared library provided by the attacker, without dropping privileges.
Using the -R command line argument, an attacker can specify a shared
library used to parse data coming from the printer.

III. ANALYSIS

Exploitation of this vulnerability results in the execution of arbitrary
code with root privileges.

The pioout program is setuid root, and executable by any user with local
access. To exploit the vulnerability, all an attacker has to do is
create a shared library that executes a shell.

IV. DETECTION

iDefense has confirmed the existence of this vulnerability in AIX
version 5.3 with service pack 6. Previous versions may also be
affected.

V. WORKAROUND

Removing the setuid bit from the binary will prevent exploitation, but
may make the program unusable by non-root users.

VI. VENDOR RESPONSE

IBM Corp. has addressed this vulnerability by releasing interim fixes.
More information can be found via the Bulletins tab of IBM's
Subscription Service for UNIX and Linux servers. You can reach this
service by clicking the URL shown below.

http://www14.software.ibm.com/webapp/set2/subscriptions/pqvcmjd?mode=1 

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2007-4003 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

06/05/2007  Initial vendor notification
06/08/2007  Initial vendor response
07/26/2007  Coordinated public disclosure

IX. CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

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X. LEGAL NOTICES

Copyright =A9 2007 iDefense, Inc.

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at the time of publishing based on currently available information. Use
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