IBM AIX capture Terminal Control Sequence Buffer Overflow Vulnerability

iDefense Security Advisory 07.26.07
http://labs.idefense.com/intelligence/vulnerabilities/
Jul 26, 2007

I. BACKGROUND

The capture program is a setuid root application, installed by default
under multiple versions of IBM AIX, that allows terminal sessions to be
dumped to a file. More information can be found at the following URL.

http://publib.boulder.ibm.com/infocenter/pseries/v5r3/topic/com.ibm.aix.cmds/doc/aixcmds1/capture.htm

II. DESCRIPTION

Local exploitation of a stack-based buffer overflow vulnerability in the
'capture' program, as included with IBM Corp.'s AIX operating system,
allows an attacker to execute arbitrary code with root privileges.

The vulnerability exists within the code that parses terminal control
sequences. A long series of control sequences will trigger an
exploitable stack-based buffer overflow.

III. ANALYSIS

Exploitation of this vulnerability results in the execution of arbitrary
code with root privileges.

The capture program is setuid root, and executable by any user with
local access. The vulnerability is a stack-based buffer overflow, and
is trivially exploitable.

IV. DETECTION

iDefense has confirmed the existence of this vulnerability in AIX
version 5.3 with service pack 6. Previous versions may also be
affected.

V. WORKAROUND

Removing the setuid bit from the binary will prevent exploitation, but
may make the program unusable by non-root users.

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-2007-3333 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

06/05/2007  Initial vendor notification
06/08/2007  Initial vendor response
07/26/2007  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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