The chdev program is a setuid root application, installed by default
under multiple versions of IBM AIX, that facilitates the changing of
Local exploitation of a format string vulnerability in the chdev 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 improperly used
formatted printing function. When provided with an incorrect argument
(argv) 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.
This vulnerability can only be exploited by a local user who has been
granted access to the "system" group. Successful exploitation leads to
Due to the nature of the vulnerability, information leakage is trivial
and aids the attacker in exploitation.
iDEFENSE has confirmed the existence of this vulnerability in IBM AIX
version 5.2. It is suspected that previous versions are also vulnerable.
Only allow trusted users local access to security critical systems. Only
allow trusted system administrators access to the "system" group.
Alternately, remove the setuid bit from chdev using chmod u-s
The vendor has not released a patch for this issue, however, the
following details have been published:
In addition, a security advisory will be posted at the following site:
Please note that a free signup is required to access the security
The Common Vulnerabilities and Exposures (CVE) project has assigned the
names CAN-2005-0240 to these issues. This is a candidate for inclusion
in the CVE list (http://cve.mitre.org), which standardizes names for
12/21/2004 Initial vendor notification
01/07/2005 Initial vendor response
02/07/2005 Coordinated public disclosure
iDEFENSE Labs is credited with this discovery.
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