Vulnerability Note VU#896729

IBM AIX auditselect contains format string vulnerability

Overview

IBM AIX auditselect command contains a format string vulnerability that may allow a local attacker to execute arbitrary code.

I. Description

According to IBM's Command Reference, the syntax and description of the auditselect command are as follows:

$> auditselect { -e "Expression" | -f File} [ -m ] [ Trail ]

The auditselect command is part of the audit subsystem. The command is called by the auditbin daemon if it is configured in the /etc/security/audit/bincmds file as a backend command for processing bin files.

The auditselect command selects audit records that match identified criteria and writes the records to standard output. With the auditselect command, you can filter the audit trail to obtain specific records for analysis or select specific records for long-term storage. The command takes stream or bin input from the file specified by the Trail parameter or from standard input. If you specify the $bin string as the value of the Trail parameter, the auditbin daemon substitutes the path name of the current bin file when it calls the auditselect command. The selection criteria can be entered as an expression or from the file specified by the -f flag. If the bin files are compressed, the auditselect command unpacks them prior to processing.

There is a format string vulnerability within the auditselect command due to the way it uses formatted output routines, such as printf(). The auditselect command may pass formatted output routines user-supplied data. If a local attacker with audit group membership passes a specially crafted parameter to auditselect, that parameter may be passed to a formatted output routine. Since output routines in auditselect do not adequately filter or restrict input (via a format string specifier), the attacker may be able to exploit this vulnerability.

Please note that the auditselect command executes with root privileges.

II. Impact

By supplying auditselect specially crafted input, a local attacker with membership in the audit group may be able to execute arbitrary code with root privileges.

III. Solution

We are currently unaware of a practical solution to this problem.

Workaround

Restrict Access to Audit Group

To successfully exploit this vulnerability an attacker must have access to the audit group. By restricting membership to the audit group to trusted users, the chances of exploitation are reduced.

Systems Affected

Vendor	Status	Date Notified	Date Updated
IBM	Vulnerable	28-Feb-2005

References

http://www-1.ibm.com/support/docview.wss?uid=isg1IY67519
http://www.idefense.com/application/poi/display?id=193&type=vulnerabilities
http://www.securiteam.com/unixfocus/5OP0G15EUU.html
http://secunia.com/advisories/14198/

Credit

This vulnerability was reported by iDEFENSE Security.

This document was written by Jeff Gennari.

Other Information

Date Public:	2005-02-08
Date First Published:	2005-02-28
Date Last Updated:	2005-02-28
CERT Advisory:
CVE-ID(s):	CAN-2005-0250
NVD-ID(s):	CAN-2005-0250
US-CERT Technical Alerts:
Metric:	1.01
Document Revision:	75

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