SCO Openserver authsh 'Home' Buffer Overflow Vulnerability
iDEFENSE Security Advisory 10.24.05
http://www.idefense.com/application/poi/display?type=vulnerabilities
October 24, 2005
I. BACKGROUND
SCO OpenServer is a UNIX-like operating system for x86 platforms.
II. DESCRIPTION
Local exploitation of a buffer overflow vulnerability in The SCO Group
Inc.'s Openserver operating system could allow an attacker to gain root
privileges.
The authsh utility is a standard binary distributed with the Openserver
platform. The vulnerability specifically exists because of a lack of
bounds checking on the value given to the "HOME" environment variable.
Local attackers can supply a specially crafted string to overflow a
stack buffer and execute arbitrary code with group auth privileges.
III. ANALYSIS
Successful exploitation of this vulnerability will result in execution
of arbitrary code with permissions of the running process. The binary is
setgid auth by default and can be used by attackers with a local account
to gain root privileges, as the group auth has write access to system
authentication information. An attacker would only need to modify the
system passwd file to grant an account they control superuser
privileges.
IV. DETECTION
iDEFENSE has confirmed the existence of this vulnerability in SCO
Openserver 5.0.7. It is suspected that earlier versions are also
vulnerable.
V. WORKAROUND
As a workaround solution, remove the setgid bit from the authsh binary
until a vendor patch can be applied.
# chmod -g /opt/K/SCO/Unix/5.0.7Hw/usr/lib/sysadm/authsh
VI. VENDOR RESPONSE
The vendor has released the following advisory for this issue:
ftp://ftp.sco.com/pub/updates/OpenServer/SCOSA-2005.40/SCOSA-2005.40.txt
VII. CVE INFORMATION
The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2005-2926 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org), which standardizes names for
security problems.
VIII. DISCLOSURE TIMELINE
09/08/2005 Initial vendor notification
09/09/2005 Initial vendor response
10/24/2005 Public disclosure
IX. CREDIT
iDEFENSE Labs is credited with the discovery of this vulnerability.
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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.
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