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TUCoPS :: Linux :: General :: ciacg038.txt

mount umount vulns


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

                             INFORMATION BULLETIN

              Linux Vulnerabilities in mount and umount Programs

August 15, 1996 16:00 GMT                                          Number G-38
PROBLEM:       A security hole has been identified in the mount and umount
PLATFORM:      All systems running current distributions of Linux including
               all versions of Red Hat Linux.
DAMAGE:        This vulnerability may allow any user with an account
               on a system to obtain root access.
SOLUTION:      Read and implement the workaround and/or patches described
VULNERABILITY  This vulnerability is becoming widely known. CIAC recommends
ASSESSMENT:    implementing the workaround and/or patches as soon as possible.

The mount and umount programs are normally installed with setUID root to 
allow users to perform mount and unmount operations. However, they do not 
check the length of the information being passed, thereby creating a buffer 
overflow problem.

Operating Systems Tested: All current distributions of Linux

Effect: Local users on systems affected can gain overflow mounts syntax 
buffer and execute a shell by overwriting the stack.

Effected binaries:
(/bin/mount and /bin/umount)

On all current distributions of Linux remove suid bit of /bin/mount and 
[chmod -s /bin/mount; chmod -s /bin/umount]

Operating Systems Tested: All versions of Red Hat Linux

Users of versions of Red Hat less than 3.0.3 are advised to upgrade to
3.0.3, since many other problems are fixed in the upgrade.

If you are running:
* Red Hat Linux 3.0.3 (Picasso) on the Intel architecture, get
And install them in that order using 'rpm -Uvh [rpm filename]'

* Red Hat Linux 3.0.3 (Picasso) on the Alpha architecture, get
And install them in that order using 'rpm -Uvh [rpm filename]'

* Red Hat Linux 3.0.4 (Rembrandt) beta on the Intel, get

* Red Hat Linux 3.0.4 (Rembrandt) beta on the Sparc, get

[Aside: There is no difference between mount-2.5k-1 and -2 except
the package format.]

All RPMs are PGP-signed with the key.
The source RPMs will be available in the normal locations.

ad9b0628b6af9957d7b5eb720bbe632b  mount-2.5k-1.axp.rpm
12cb19ec4b3060f8d1cedff77bda7c05  util-linux-2.5-11fix.axp.rpm

26506a3c0066b8954d80deff152e0229  mount-2.5k-1.i386.rpm
f48c6bf901dd5d2c476657d6b75b12a5  util-linux-2.5-11fix.i386.rpm

7337f8796318f3b13f2dccb4a8f10b1a  mount-2.5k-2.i386.rpm
e68ff642a7536f3be4da83eedc14dd76  mount-2.5k-2.sparc.rpm

Thanks to Bloodmask, Vio, and others on the BugTraq list for discovering
this hole and providing patches.


CIAC wishes to acknowledge the contributions of Bloodmask, Vio, Elliot Lee at 
Red Hat, and others on BugTraq 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.

CIAC services are available to DOE, DOE contractors, and the NIH. CIAC
can be contacted at:
    Voice:    +1 510-422-8193
    FAX:      +1 510-423-8002
    STU-III:  +1 510-423-2604

For emergencies and off-hour assistance, DOE, DOE contractor sites,
and the NIH may contact CIAC 24-hours a day. During off hours (5PM -
8AM PST), call the CIAC voice number 510-422-8193 and leave a message,
or call 800-759-7243 (800-SKY-PAGE) to send a Sky Page. CIAC has two
Sky Page PIN numbers, the primary PIN number, 8550070, is for the CIAC
duty person, and the secondary PIN number, 8550074 is for the CIAC
Project Leader.

Previous CIAC notices, anti-virus software, and other information are
available from the CIAC Computer Security Archive.

   World Wide Web:
   Anonymous FTP: (
   Modem access:        +1 (510) 423-4753 (28.8K baud)
                        +1 (510) 423-3331 (28.8K baud)

CIAC has several self-subscribing mailing lists for electronic
1. CIAC-BULLETIN for Advisories, highest priority - time critical
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2. CIAC-NOTES for Notes, a collection of computer security articles;
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   (SPI) software updates, new features, distribution and
4. SPI-NOTES, for discussion of problems and solutions regarding the
   use of SPI products.

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You will receive an acknowledgment containing address, initial PIN,
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PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing
communities receive CIAC bulletins.  If you are not part of these
communities, please contact your agency's response team to report
incidents. Your agency's team will coordinate with CIAC. The Forum of
Incident Response and Security Teams (FIRST) is a world-wide
organization. A list of FIRST member organizations and their
constituencies can be obtained by sending email to with an empty subject line and a message body
containing the line: send first-contacts.

This document was prepared as an account of work sponsored by an
agency of the United States Government. Neither the United States
Government nor the University of California nor any of their
employees, makes any warranty, express or implied, or assumes any
legal liability or responsibility for the accuracy, completeness, or
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disclosed, or represents that its use would not infringe privately
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