IBM AIX ipl_varyon Local Buffer Overflow Vulnerability

iDEFENSE Security Advisory 02.10.05
www.idefense.com/application/poi/display?id=196&type=vulnerabilities
February 10, 2005

I. BACKGROUND

The ipl_varyon program is a setuid root application, installed by
default under multiple versions of IBM AIX, which can be used to set the

default physical boot volume.

II. DESCRIPTION

Local exploitation of a buffer overflow vulnerability in the ipl_varyon
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 unbounded
string copy operation. When provided with a long argument to the -d
option, the ipl_varyon process will overwrite stack memory with the user

supplied string. This allows for overwriting of the saved return address

on the stack, which in turn allows for complete control over execution
flow.

III. ANALYSIS

Exploitation of this vulnerability is simple for a skilled attacker,
however gid "system" is required in order to execute the vulnerable
binary. Successful exploitation yields root access on the system.

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 users access to the "system" group. Alternately, remove
the setuid bit from netpmon using chmod u-s /usr/sbin/ipl_varyon

VI. VENDOR RESPONSE

Vendor advisories for this issue are available at:

For AIX 5.1:

https://techsupport.services.ibm.com/server/pseries.subscriptionSvcs?mod

e=1&heading=AIX51&topic=SECURITY&month=ALL

For AIX 5.2:

https://techsupport.services.ibm.com/server/pseries.subscriptionSvcs?mod

e=1&heading=AIX52&topic=SECURITY&month=ALL

For AIX 5.3:

https://techsupport.services.ibm.com/server/pseries.subscriptionSvcs?mod

e=1&heading=AIX53&topic=SECURITY&month=ALL

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
01/07/2004 Initial vendor response
02/10/2004 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
email customerservice (at) idefense (dot) com [email concealed] for permission.

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.

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