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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