‘IBM AIX auditselect Local Format String Vulnerability’

Summary

‘The auditselect program is ‘a setuid root application, installed by default under multiple versions of IBM AIX, that selects audit records for analysis according to defined criteria’.

Local exploitation of a format string vulnerability in the auditselect command included by default in multiple versions of IBM Corp.’s AIX operating system could allow for arbitrary code execution as the root user.’

Credit:

‘The information has been provided by iDEFENSE Customer Service.
The original article can be found at: http://www.idefense.com/application/poi/display?id=193&type=vulnerabilities


Details

Vulnerable Systems:
 * IBM AIX version 5.2
 * IBM AIX version 5.3

The vulnerability specifically exists due to an improperly used formatted printing function. When provided with an incorrect argument (argv[1]) that contains a format string, the format string will be fed into a formatted printing function, and the user supplied format string will be evaluated, allowing for a malicious user to examine stack memory and write to arbitrary memory locations. With a properly crafted string, this can lead to the execution of arbitrary code.

Analysis:
This vulnerability can only be exploited by a local user who has been granted access to the ‘audit’ group. Successful exploitation leads to root-level access.

Due to the nature of the vulnerability, information leakage is trivial and aids the attacker in exploitation.

Workaround:
Only allow trusted users local access to security critical systems. Only allow trusted system administrators access to the ‘audit’ group. Alternately, remove the setuid bit from auditselect using chmod u-s /usr/sbin/auditselect.

Vendor Status:
The vendor has not released a patch for this issue, however, the following details have been published:
   http://www-1.ibm.com/support/docview.wss?uid=isg1IY67519

Disclosure Timeline:
12/21/2004 – Initial vendor notification
01/07/2005 – Initial vendor response
02/08/2005 – Public disclosure’

Categories: UNIX