Public Vulnerability Reports

IBM AIX invscout Local Command Execution Vulnerability

12.20.04

BACKGROUND

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).

DESCRIPTION

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
/usr/sbin/invscout.

ANALYSIS

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.

DETECTION

iDEFENSE has confirmed the existence of this vulnerability in IBM AIX
version 5.2.0.

WORKAROUND

Only allow trusted users local access to security critical systems.
Alternately, remove the setuid bit from invscout using chmod u-s
/usr/sbin/invscout.

VENDOR RESPONSE

"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."

CVE INFORMATION

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
security problems.

DISCLOSURE TIMELINE

11/12/2004 Initial vendor notification
11/18/2004 Initial vendor response
12/20/2004 Coordinated public disclosure

CREDIT

iDEFENSE Labs is credited with this discovery.

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LEGAL NOTICES

Copyright © 2004 Verisign, Inc.

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Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
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There are no warranties with regard to this information. Neither the
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