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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