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.

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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
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There are no warranties with regard to this information. Neither the
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