IBM AIX dig dns_name_fromtext Integer Underflow Vulnerability

iDefense Security Advisory 10.30.07
http://labs.idefense.com/intelligence/vulnerabilities/
Oct 30, 2007

I. BACKGROUND

dig is a utility that is commonly used for DNS diagnostics. Under AIX
5.2, the dig program is installed by default and is set-uid root. More
information can be found at the URL shown.

http://publib.boulder.ibm.com/infocenter/pseries/v5r3/topic/com.ibm.aix.cmds/doc/aixcmds2/dig.htm

II. DESCRIPTION

Local exploitation of an integer underflow vulnerability in the dig
program of IBM Corp.'s AIX operating system allows attackers to execute
arbitrary code with root privileges.

The problem specifically exists within dns_name_fromtext function within
the libdns.a library. This function is called when processing the '-y'
command line parameter to the dig program. By supplying a specially
crafted TSIG key parameter, an attacker is able to cause an integer
underflow, resulting in potentially exploitable heap corruption.

III. ANALYSIS

Exploitation allows an attacker to execute arbitrary code with root
privileges. Local access is required to execute the dig program.

It should be noted that this particular issue is documented within the
bind release notes as bug #1211 and #1350. However, this particular
vulnerability is specific to AIX 5.2 since it installs the dig program
set-uid root.

IV. DETECTION

iDefense has confirmed the existence of this vulnerability within AIX
version 5.2. Previous versions are suspected to be vulnerable. AIX 5.3
is not vulnerable since the dig command is no longer installed set-uid
root.

V. WORKAROUND

Removing the set-uid bit from the dig program will prevent exploitation.

VI. VENDOR RESPONSE

IBM Corp. has addressed this vulnerability by releasing interim fixes.
More information can be found via the Bulletins tab of IBM's
Subscription Service for UNIX and Linux servers. You can reach this
service by clicking the URL shown below.

http://www14.software.ibm.com/webapp/set2/subscriptions/pqvcmjd?mode=1

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2007-4622 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

08/30/2007  Initial vendor notification
09/14/2007  Initial vendor response
10/30/2007  Coordinated public disclosure

IX. CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

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X. LEGAL NOTICES

Copyright © 2007 iDefense, Inc.

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at the time of publishing based on currently available information. Use
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