Public Vulnerability Reports

Multiple Vendor wvWare LFO Count Integer Overflow Vulnerability

10.26.06

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/

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.

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.

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.

WORKAROUND

Users should avoid opening suspicious documents from untrusted sources.

VENDOR RESPONSE

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

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.

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

CREDIT

This vulnerability was reported to iDefense by infamous41md.

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LEGAL NOTICES

Copyright © 2006 Verisign, Inc.

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