Multiple Vendor wvWare LFO Count Integer Overflow Vulnerability

iDefense Security Advisory 10.26.06
http://www.idefense.com/intelligence/vulnerabilities/
Oct 26, 2006

I. BACKGROUND

The WV library provides an interface to facilitate access to binary file
format Microsoft Word documents. The project was originally called
"mswordview" but was renamed to avoid confusion. For more information,
see http://wvware.sourceforge.net/

II. DESCRIPTION

Remote exploitation of an integer overflow vulnerability in the WV
library could allow an attacker to execute arbitrary code.

When parsing documents, two user supplied integer values are multiplied
without checking for an overflow condition.

    89  int
    90  wvGetLFO_PLF (LFO ** lfo, U32 * nolfo, U32 offset, U32 len,
wvStream * fd)
   ...
   101            *nolfo = read_32ubit (fd);
   ...
   104            *lfo = (LFO *) wvMalloc (*nolfo * sizeof (LFO));
   ...
   112            for (i = 0; i < *nolfo; i++)
   113                wvGetLFO (&((*lfo)[i]), fd);


As can be seen from the source code above, an attacker supplied integer
value is read from the file on line 101. On line 104, memory for that
number of structures is allocated based on the supplied number
multiplied by the size of the structures. Any value larger than 2^^32 /
sizeof(LFO) will cause an integer overflow. Lines 112 and 113 show the
loop used for reading data into the newly allocated heap buffer.  When
integer overflow occurs, the loop will store data beyond the end of the
allocated heap buffer.

III. ANALYSIS

A remote attacker could execute arbitrary code as a user that uses a WV
library dependent product to handle a malicious Microsoft Word document.

IV. DETECTION

iDefense has confirmed that this vulnerability exists in version 1.2.2
of the WV library. Earlier versions are suspected to be vulnerable as
well.

V. WORKAROUND

Users should avoid opening suspicious documents from untrusted sources.

VI. VENDOR RESPONSE

The wvWare maintainers have addressed this vulnerability by releasing
version 1.2.3.

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2006-4513 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

08/17/2006  Initial vendor notification
10/18/2006  Initial vendor response
10/18/2006  Second vendor notification
10/26/2006  Coordinated public disclosure

IX. CREDIT

This vulnerability was reported to iDefense by infamous41md.

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X. LEGAL NOTICES

Copyright © 2006 iDefense, Inc.

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