iDefense Security Advisory 04.17.08: Multiple Vendor OpenOffice QPRO File Parsing Integer Underflow Vulnerability

iDefense Security Advisory 04.17.08
http://labs.idefense.com/intelligence/vulnerabilities/
Apr 17, 2008

I. BACKGROUND

OpenOffice is an open-source desktop office suite for many of today's
popular operating systems. One of the file formats that OpenOffice
supports is Quattro Pro (QPRO). This format is used by Corel's
QuattroPro spreadsheet application. More information is available from
the following URL.

http://www.openoffice.org/

II. DESCRIPTION

Remote exploitation of an integer underflow vulnerability in OpenOffice,
as included in various vendors' operating system distributions, allows
attackers to execute arbitrary code with the privileges of the logged
in user.

The vulnerability exists within the code responsible for converting the
QPRO file into an internal representation used by OpenOffice. A 16-bit
integer is read in from the file, and later used as a loop counter that
controls how many values are stored into local stack buffers. When
verifying the value of this counter, the code decrements the counter
without checking to see if this operation will underflow. This results
in the loop running for many iterations, which leads to a stack based
buffer overflow. This allows for the execution of arbitrary code.

III. ANALYSIS

Exploitation of this vulnerability results in the execution of arbitrary
code with the privileges of the user opening the file. In order to
exploit this vulnerability, an attacker must persuade a user to open a
malicious file.

IV. DETECTION

iDefense has confirmed the existence of this vulnerability in OpenOffice
version 2.3. Other versions may also be affected.

V. WORKAROUND

Renaming the shared library that contains the vulnerable code will
prevent OpenOffice from opening QPRO files. On Fedora Core 7, the
library can be found at:

/usr/lib/openoffice.org/program/libsc680li.so

Renaming this file to libsc680li.so.bak will prevent it from being
loaded. In addition to preventing the use of QPRO files, this also
prevents users from opening various other file formats.

VI. VENDOR RESPONSE

The OpenOffice.org team has addressed this vulnerability with the
release of version 2.4. For more information, consult the OOo Security
Bulletin at the following URL.

http://www.openoffice.org/security/cves/CVE-2007-5745.html

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2007-5747 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

10/29/2007 Initial vendor notification
10/30/2007 Initial vendor response
04/17/2008 Coordinated public disclosure

IX. CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

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X. LEGAL NOTICES

Copyright © 2008 iDefense, 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
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
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