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CIAC Bulletin H-27: HP-UX vgdisplay Buffer Overrun Vulnerability
From: aleph1 () DFW NET (Aleph One)
Date: Sat, 15 Feb 1997 13:53:13 -0600



                       The U.S. Department of Energy
                    Computer Incident Advisory Capability
                           ___  __ __    _     ___
                          /       |     /_\   /
                          \___  __|__  /   \  \___

                             INFORMATION BULLETIN

                  HP-UX vgdisplay Buffer Overrun Vulnerability

February 7, 1997 22:00 GMT                                         Number H-27
PROBLEM:       A vulnerability exists in the vgdisplay(1M) program which is
               part of the Logical Volume Manager subsystem.
PLATFORM:      HP-UX 10.x.
DAMAGE:        This vulnerability may allow local users to gain root
SOLUTION:      Until patches are available, it is recommended that sites take
               the steps outlined in section 3 as soon as possible.
VULNERABILITY  Exploit details involving this vulnerability have been made
ASSESSMENT:    publicly available.

[ Start AUSCERT Advisory ]

AA-97.04                        AUSCERT Advisory
                  HP-UX vgdisplay Buffer Overrun Vulnerability
                                7 February 1997

Last Revised: --

- --------------------------------------------------------------------------
AUSCERT has received information that a vulnerability exists in the
vgdisplay(1M) program which is part of the Logical Volume Manager subsystem
under HP-UX 10.x.

This vulnerability may allow local users to gain root privileges.

Exploit information involving this vulnerability has been made publicly

Currently there are no vendor patches available that address this
vulnerability.  AUSCERT recommends that sites take the steps outlined in
section 3 as soon as possible.

This advisory will be updated as more information becomes available.
- --------------------------------------------------------------------------

1.  Description

    The HP-UX Logical Volume Manager (LVM) is a subsystem for managing
    disk space.  It comprises a number of auxiliary programs used to
    create, display and manipulate the LVM information.

    AUSCERT has received information that a vulnerability exists in the
    vgdisplay(1M) program used to display information about LVM volume

    Due to insufficient bounds checking on arguments which are supplied
    by users, it is possible to overwrite the internal stack space of the
    vgdisplay program while it is executing.  By supplying a carefully
    designed argument to the vgdisplay program, intruders may be able to
    force vgdisplay to execute arbitrary commands.  As vgdisplay is setuid
    root, this may allow intruders to run arbitrary commands with root

    This vulnerability is known to affect HP-UX 10.x.

    Note that many of the LVM utility programs are hard links to
    vgdisplay(1M).  This indicates that these utility programs share the
    same code with vgdisplay, and may also be subject to similar attacks.

    The following programs are all hard links: lvchange, lvcreate,
    lvdisplay, lvextend, lvlnboot, lvreduce, lvremove, lvrmboot, pvchange,
    pvcreate, pvdisplay, pvmove, vgcfgbackup, vgcfgrestore, vgchange,
    vgcreate, vgdisplay, vgexport, vgextend, vgimport, vgreduce, vgremove,

    By default, dynamically linked versions of the LVM programs are found
    in /usr/sbin under HP-UX 10.x.  Statically linked versions are also
    available under HP-UX 10.x in /sbin.

    Exploit information involving this vulnerability has been made
    publicly available.

2.  Impact

    Local users may gain root privileges.

3.  Workarounds/Solution

    AUSCERT recommends that sites limit the possible exploitation of this
    vulnerability by immediately removing the setuid permissions as stated
    in Section 3.1.

    Currently there are no vendor patches available that address this
    vulnerability.  AUSCERT recommends that official vendor patches be
    installed when they are made available.

3.1 Remove setuid and non-root execute permissions

    To prevent the exploitation of the vulnerability described in this
    advisory, AUSCERT recommends that the setuid permissions be removed
    from the vgdisplay program immediately.  Note that permission changes
    to vgdisplay will also affect those LVM utility programs which are
    hard links to vgdisplay.

    As the vgdisplay and related programs will no longer work for non-root
    users, it is recommended that the execute permissions also be removed.

    Sites will need to restrict permissions on both the dynamically linked
    copies in /usr/sbin and the statically linked copies in /sbin.

    First, restrict permissions on the copies in /usr/sbin.  For example:

        # ls -l /usr/sbin/vgdisplay
        -r-sr-xr-x  23 root   sys  376832 Jun 10  1996 /usr/sbin/vgdisplay

        # chmod 500 /usr/sbin/vgdisplay
        # ls -l /usr/sbin/vgdisplay
        -r-x------  23 root   sys  376832 Jun 10  1996 /usr/sbin/vgdisplay

    Second, restrict permissions on the copies in /sbin.  For example:

        # ls -l /sbin/vgdisplay
        -r-sr-xr-x  23 root   sys  606208 Jun 10  1996 /sbin/vgdisplay

        # chmod 500 /sbin/vgdisplay
        # ls -l /sbin/vgdisplay
        -r-x------  23 root   sys  606208 Jun 10  1996 /sbin/vgdisplay

    Note that this will remove the ability for any non-root user to run
    vgdisplay or any of the LVM utility programs which are hard linked to

4.  Previous patches

    During the installation of HP-UX patches, copies of files being
    replaced are saved in case the patches need to be backed out of.  The
    original versions of patched files are often stored in the following

        HP-UX 10.x:     /var/adm/sw/patch/<PATCH_NAME>/

    If patches for vulnerable programs have been previously installed,
    copies of the vulnerable programs may be available in the above
    location.  Sites should ensure the directories have permissions
    which restrict access to the patch areas.

5.  Additional measures

    Most Unix systems ship numerous programs which have setuid or
    setgid privileges.  Often the functionality supplied by these
    privileged programs is not required by many sites.  The large number
    of privileged programs that are shipped by default are to cater for
    all possible uses of the system.

    AUSCERT encourages sites to examine all the setuid/setgid programs
    and determine the necessity of each program.  If a program does not
    absolutely require the setuid/setgid privileges to operate (for
    example, it is only run by the root user),  the setuid/setgid
    privileges should be removed.  Furthermore, if a program is not
    required at your site, then all execute permissions should be removed.

    A sample command to find all setuid/setgid programs is (run as root):

       # find / \( -perm -4000 -o -perm -2000 \) -exec ls -ld {} \;

    It is AUSCERT's experience that many vulnerabilities are being
    discovered in setuid/setgid programs which are not necessary for the
    correct operation of most systems.  Sites can increase their security
    by removing unnecessary setuid/setgid programs.

[ End AUSCERT Advisory ]

CIAC wishes to acknowledge the contributions of AUSCERT and Hewlett-Packard for
the information contained in this bulletin.

CIAC, the Computer Incident Advisory Capability, is the computer
security incident response team for the U.S. Department of Energy
(DOE) and the emergency backup response team for the National
Institutes of Health (NIH). CIAC is located at the Lawrence Livermore
National Laboratory in Livermore, California. CIAC is also a founding
member of FIRST, the Forum of Incident Response and Security Teams, a
global organization established to foster cooperation and coordination
among computer security teams worldwide.

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Version: 2.6.2


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