Public Vulnerability Reports

IBM AIX ipl_varyon Local Buffer Overflow Vulnerability

02.10.05

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.

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.

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.

DETECTION

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

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

VENDOR RESPONSE

Vendor advisories for this issue are available at:

For AIX 5.1:

https://techsupport.services.ibm.com/server/pseries.subscriptionSvcs?mode=1&heading=AIX51&topic=SECURITY&month=ALL

For AIX 5.2:

https://techsupport.services.ibm.com/server/pseries.subscriptionSvcs?mode=1&heading=AIX52&topic=SECURITY&month=ALL

For AIX 5.3:

https://techsupport.services.ibm.com/server/pseries.subscriptionSvcs?mode=1&heading=AIX53&topic=SECURITY&month=ALL

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
names CAN-2005-0262 to these issues. This is a candidate for inclusion
in the CVE list (http://cve.mitre.org), which standardizes names for
security problems.

DISCLOSURE TIMELINE

12/21/2004   Initial vendor notification
01/07/2004   Initial vendor response
02/10/2004   Coordinated public disclosure

CREDIT

iDEFENSE Labs is credited with this discovery

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LEGAL NOTICES

Copyright © 2005 Verisign, Inc.

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