[Full-Disclosure] iDEFENSE Security Advisory 02.07.05: IBM AIX chdev Local Format String Vulnerability

idlabs-advisories_at_idefense.com
Date: 02/08/05

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    Date: Mon, 7 Feb 2005 18:18:43 -0500
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    IBM AIX chdev Local Format String Vulnerability

    iDEFENSE Security Advisory 02.07.05
    http://www.idefense.com/application/poi/display?type=vulnerabilities
    February 07, 2005

    I. BACKGROUND

    The chdev program is a setuid root application, installed by default
    under multiple versions of IBM AIX, that facilitates the changing of
    device characteristics.

    II. DESCRIPTION

    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[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.

    III. ANALYSIS

    This vulnerability can only be exploited by a local user who has been
    granted access to the "system" 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.

    IV. DETECTION

    iDEFENSE has confirmed the existence of this vulnerability in 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. Only

    allow trusted system administrators access to the "system" group.
    Alternately, remove the setuid bit from chdev using chmod u-s
    /usr/sbin/chdev.

    VI. VENDOR RESPONSE

    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=isg1IY67455

    In addition, a security advisory will be posted at the following site:

    https://techsupport.services.ibm.com/server/pseries.subscriptionSvcs?mod
    e=1

    Please note that a free signup is required to access the security
    advisory.

    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
    02/07/2005 Coordinated public disclosure

    IX. CREDIT

    iDEFENSE Labs is credited with this discovery.

    Get paid for vulnerability research
    http://www.idefense.com/poi/teams/vcp.jsp

    X. LEGAL NOTICES

    Copyright (c) 2005 iDEFENSE, Inc.

    Permission is granted for the redistribution of this alert
    electronically. It may not be edited in any way without the express
    written consent of iDEFENSE. If you wish to reprint the whole or any
    part of this alert in any other medium other than electronically, please
    email customerservice@idefense.com for permission.

    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.

    _______________________________________________
    Full-Disclosure - We believe in it.
    Charter: http://lists.netsys.com/full-disclosure-charter.html


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