IBM AIX chdev Local Format String Vulnerability
iDEFENSE Security Advisory 02.07.05
http://www.idefense.com/application/poi/display?type=vulnerabilities
February 07, 2005
I. BACKGROUND
The chdev program is a setuid root application, installed by default
under multiple versions of IBM AIX, that facilitates the changing of
device characteristics.
II. DESCRIPTION
Local exploitation of a format string vulnerability in the chdev 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 "system" 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.
V. WORKAROUND
Only allow trusted users local access to security critical systems. Only
allow trusted system administrators access to the "system" group.
Alternately, remove the setuid bit from chdev using chmod u-s
/usr/sbin/chdev.
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=isg1IY67455
In addition, a security advisory will be posted at the following site:
https://techsupport.services.ibm.com/server/pseries.subscriptionSvcs?mod
e=1
Please note that a free signup is required to access the security
advisory.
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
02/07/2005 Coordinated 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.
Permission is granted for the redistribution of this alert
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part of this alert in any other medium other than electronically, please
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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.
