iDEFENSE Security Advisory 02.08.05: IBM AIX auditselect Local Format String Vulnerability

["iDefense Customer Service" <customerservice@xxxxxxxxxxxx>]

IBM AIX auditselect Local Format String Vulnerability 

iDEFENSE Security Advisory 02.08.05
www.idefense.com/application/poi/display?id=193&type=vulnerabilities
February 08, 2005

I. BACKGROUND

The auditselect program is a setuid root application, installed by 
default under multiple versions of IBM AIX, that selects audit records 
for analysis according to defined criteria. 

II. DESCRIPTION

Local exploitation of a format string vulnerability in the auditselect 
command included by default in multiple versions of IBM Corp.'s AIX 
operating system could allow for arbitrary code execution as the root 
user. 

The vulnerability specifically exists due to an improperly used 
formatted printing function. When provided with an incorrect argument 
(argv[1]) that contains a format string, the format string will be fed 
into a formatted printing function, and the user supplied format string 
will be evaluated, allowing for a malicious user to examine stack memory

and write to arbitrary memory locations. With a properly crafted string,

this can lead to the execution of arbitrary code.

III. ANALYSIS

This vulnerability can only be exploited by a local user who has been 
granted access to the "audit" group. Successful exploitation leads to 
root-level access. 

Due to the nature of the vulnerability, information leakage is trivial 
and aids the attacker in exploitation.

IV. DETECTION

iDEFENSE has confirmed the existence of this vulnerability in IBM AIX 
version 5.2. It is suspected that previous versions are also vulnerable.

IBM has reported that AIX 5.3 is also vulnerable.

V. WORKAROUND

Only allow trusted users local access to security critical systems. Only

allow trusted system administrators access to the "audit" group. 
Alternately, remove the setuid bit from auditselect using chmod u-s 
/usr/sbin/auditselect. 

VI. VENDOR RESPONSE

The vendor has not released a patch for this issue, however, the
following details have been published:

   http://www-1.ibm.com/support/docview.wss?uid=isg1IY67519

VII. CVE INFORMATION

A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not
been assigned yet.

VIII. DISCLOSURE TIMELINE

12/21/2004  Initial vendor notification
01/07/2005  Initial vendor response
02/08/2005  Public disclosure

IX. CREDIT

iDEFENSE Labs is credited with this discovery.

Get paid for vulnerability research
http://www.idefense.com/poi/teams/vcp.jsp

X. LEGAL NOTICES

Copyright (c) 2005 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
author nor the publisher accepts any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on,
this information.