IBM AIX swcons Local Arbitrary File Access Vulnerability
iDefense Security Advisory 10.30.07
http://labs.idefense.com/intelligence/vulnerabilities/
Oct 30, 2007
I. BACKGROUND
The swcons program is a set-uid root application which is installed by
default on IBM AIX. It allows for console logs to be temporarily logged
to a file or device.
II. DESCRIPTION
Local exploitation of a file access vulnerability in the swcons command
included in multiple versions of IBM Corp.'s AIX could allow for the
creation or modification of arbitrary files anywhere on the system.
The vulnerability specifically exists due to a lack of sanity checking
when using the -p option. If a user specifies a file with the -p
option, the contents of that file will be overwritten with 65,535 bytes
of uncontrolled data. If the file doesn't exist, it will be created. In
both cases, the file will also be converted to mode 222, which allows
all users on the system to modify it. By specifying a system file,
users can cause a denial of service condition or elevate privileges.
III. ANALYSIS
Exploitation allows attackers to execute arbitrary code with root
privileges. The severity of this vulnerability is lessened by the fact
that under a default configuration, the group id "system" is needed to
execute swcons.
IBM originally released an interim fix on February 22nd, 2007. The
original fix did prevent attackers from being able to overwrite or
change the ownership of existing files, but did not prevent the
creation of new files via symlink attacks.
IV. DETECTION
iDefense has confirmed the existence of this vulnerability on 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.
Limit access to the "system" group. Alternately, remove the set-uid bit
from the swcons program.
VI. VENDOR RESPONSE
IBM Corp. has addressed this vulnerability by releasing interim fixes.
More information can be found via the Bulletins tab of IBM's
Subscription Service for UNIX and Linux servers. You can reach this
service by clicking the URL shown below.
http://www14.software.ibm.com/webapp/set2/subscriptions/pqvcmjd?mode=1
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
10/30/2007 Coordinated public disclosure
IX. CREDIT
This vulnerability was reported to iDefense by Alex DeLarge.
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X. LEGAL NOTICES
Copyright © 2007 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.
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