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Internet Security Systems Security Advisory
June 20, 2000

Insecure call of external program in AIX cdmount

Synopsis:
The AIX cdmount program allows regular users to mount CD-ROM filesystems.
This program is basically a SUID to root wrapper of the mount command.
Insecure handling of the arguments to cdmount may allow a local regular user
to execute commands as root.

Impact:
Local users may gain root privileges.

Affected Versions:
AIX systems with the LPP UMS.objects 2.3.0.0 and below installed. Use the
command 'lslpp -l UMS.objects' to verify if a vulnerable version is installed.

Description:
The cdmount program is part of the AIX UltiMedia Services (UMS) package. UMS
provides multimedia applications to AIX workstations. The cdmount program is
normally used as a helper to UMS multimedia players. It has SUID root
permissions to allow regular users to mount a CD-ROM. The system()library
subroutine is used within cdmount to invoke the mount program..  This
subroutine spawns a shell to execute the mount command with arguments
provided by the user. An attacker may execute arbitrary commands as root by
calling cdmount with arguments containing shell metacharacters.

Recommendations:
ISS recommends removing the SUID bit from cdmount by executing the following
command:
# chmod 555 /usr/lpp/UMS/bin/cdmount

IBM is currently working on the following APAR (Authorized Problem Analysis
Report), which will be available soon:
APAR 4.3.x:  IY10903

Until the official fix is available, if UMS is not being used IBM recommends
uninstalling UMS or removing the SUID bit from cdmount.

APARs may be ordered using Electronic Fix Distribution (via FixDist) or from
the IBM Support Center. For more information on FixDist, go to
https://service.software.ibm.com/support/rs6000 or send an email to
aixserv@austin.ibm.com with a subject of "FixDist".

Additional Information:
The Common Vulnerabilities and Exposures (CVE) project has assigned the name
CAN-2000-0466 to this issue. This is a candidate for inclusion in the CVE
list https://cve.mitre.org, which standardizes names for security problems.

Credits:
This vulnerability was discovered and researched by Oliver Atoa-Ortiz of the
ISS X-Force. ISS would like to thank IBM for their response and handling of
this vulnerability.


______

About Internet Security Systems (ISS) 
Internet Security Systems (ISS) is a leading global provider of security
management solutions for the Internet. By providing industry-leading
SAFEsuite security software, remote managed security services, and strategic
consulting and education offerings, ISS is a trusted security provider to
its customers, protecting digital assets and ensuring safe and uninterrupted
e-business. ISS' security management solutions protect more than 5,500
customers worldwide including 21 of the 25 largest U.S. commercial banks, 10
of the largest telecommunications companies and over 35 government agencies.
Founded in 1994, ISS is headquartered in Atlanta, GA, with additional
offices throughout North America and international operations in Asia,
Australia, Europe, Latin America and the Middle East. For more information,
visit the Internet Security Systems web site at www.iss.net or call
888-901-7477.

Copyright (c) 2000 Internet Security Systems, Inc.

Permission is hereby granted for the redistribution of this Alert
electronically. It is not to be edited in any way without express consent of
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Disclaimer
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NO warranties with regard to this information. In no event shall the author
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Please send suggestions, updates, and comments to X-Force: xforce@iss.net of
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Revision History 
June 20, 2000:  Initial release.

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