Multiple Vendor wvWare LVL 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, an attacker supplied integer value is multiplied
with a constant without checking for an overflow condition.

    35  int
    36  wvGetLFO_records (LFO ** lfo, LFOLVL ** lfolvl, LVL ** lvl, U32
*nolfo,
    37                    U32 * nooflvl, U32 offset, U32 len, wvStream *fd)
    38  {
    ..
    47      for (i = 0; i < *nolfo; i++)
    48          *nooflvl += (*lfo)[i].clfolvl;
    ..
    59      *lfolvl = (LFOLVL *) wvMalloc (sizeof (LFOLVL) * *nooflvl);
    60      *lvl = (LVL *) wvMalloc (sizeof (LVL) * *nooflvl);


On lines 47 and 48, a loop of '*nolfo' iterations increments '*nooflvl'
by an attacker supplied 8-bit value read from the file. Lines 59 and 60
will use the calculated value to allocate memory for two different
dynamic structure arrays. Since no input validation is done, integer
overflow can occur. If an integer overflow, or wrap-around, does occur
it will lead to a heap overflow situation.

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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