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June 21, 2000 21:00 GMT
Number K-052
PROBLEM: The cdmount program allows regular users to mount CD-ROM
filesystems. A malicious user could execute cdmount giving
commands containing shell metacharacters.
PLATFORM: AIX systems with the LPP UMS.objects 2.3.0.0 and below
installed.
DAMAGE: A malicious user can run arbitrary commands, as root, through
shell metacharacter command manipulation.
SOLUTION: IBM is currently working on the issue in APAR 4.3x: IY10903
(Authorized Problem Analysis Report). Apply one of the
temporary fixes, as suggested by the advisory.
VULNERABILITY
The risk is MEDIUM. The capability currently exists for root
ASSESSMENT: command execution.
[****** Begin ISS Advisory ******]
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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
http://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 http://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)
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Revision History
June 20, 2000: Initial release.
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