Public Vulnerability Reports

IBM AIX swcons Local Arbitrary File Access Vulnerability

10.30.07

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.

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.

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.

DETECTION

iDefense has confirmed the existence of this vulnerability on 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. Limit access to the "system" group. Alternately, remove the set-uid bit from the swcons program.

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

CVE INFORMATION

A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not been assigned yet.

DISCLOSURE TIMELINE

12/21/2004 Initial vendor notification
01/07/2005 Initial vendor response
10/30/2007 Coordinated public disclosure

CREDIT

This vulnerability was reported to iDefense by Alex DeLarge.

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LEGAL NOTICES

Copyright © 2007 Verisign, Inc.

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