The invscout program is a setuid root application, installed by default
under newer versions of IBM AIX, that surveys the host system for
currently installed microcode or Vital Product Data (VPD).
Local exploitation of an untrusted path vulnerability in the invscout
command included by default in multiple versions of IBM Corp.'s AIX
could allow attackers to execute arbitrary code as the root user.
During execution, invscout invokes an external application ("lsvpd")
without dropping privileges. This application in turn invokes another
external application ("uname"), while trusting the user-specified PATH
environment variable. As root privileges are not dropped before this
sequence of execution occurs, it is possible for an attacker to gain
root access by specifying a controlled path and creating a malicious
binary within that path. To exploit the vulnerability, an attacker needs
only to create an executable file called "uname" that contains malicious
code, set the PATH variable to the current directory and execute
Exploitation of this vulnerability allows local attackers to gain
increased privileges. Successful explication requires a local account
and a writable directory. This directory can be the user's home
directory, or even the /tmp directory. Exploitation does not require
any knowledge of application internals, making privilege escalation
trivial, even for unskilled attackers.
iDEFENSE has confirmed the existence of this vulnerability in IBM AIX
Only allow trusted users local access to security critical systems.
Alternately, remove the setuid bit from invscout using chmod u-s
"IBM provides the following fixes:
APAR number for AIX 5.1.0: IY64852 (available)
APAR number for AIX 5.2.0: IY64976 (available)
APAR number for AIX 5.3.0: IY64820 (available)
NOTE: Affected customers are urged to upgrade to 5.1.0, 5.2.0 or 5.3.0
at the latest maintenance level."
The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CAN-2004-1054 to this issues. This is a candidate for inclusion
in the CVE list (http://cve.mitre.org), which standardizes names for
11/12/2004 Initial vendor notification
11/18/2004 Initial vendor response
12/20/2004 Coordinated public disclosure
iDEFENSE Labs is credited with this discovery.
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