Public Vulnerability Reports

Multiple Vendor xzgv PRF Parsing Integer Overflow Vulnerability

12.13.04

BACKGROUND

xzgv is a picture viewer for X, with a thumbnail-based file selector. It
uses GTK+ and Imlib 1.x. Most file formats are supported, and the
thumbnails used are compatible with xv, zgv and the Gimp.

DESCRIPTION

Remote exploitation of an integer overflow vulnerability in various
vendors' implementations of the read_prf_file method in the xzgv program
could allow for arbitrary code execution. The vulnerability specifically
exists due to an integer overflow while allocating memory for an image
file. The vulnerable code is as follows:

xzgv-0.8/src/readprf.c:
if((*theimageptr=malloc(width*height*3))==NULL)
[...]

The values width and height are integers that are ultimately supplied by
the image file. With certain values for height and width set in an image
file, not enough memory is allocated due to an integer overflow. The
underallocated memory is later written to, causing heap corruption and
possible arbitrary code execution with the privileges of the user
viewing the image file.

ANALYSIS

Exploitation allows attackers to gain the privileges of the user viewing
the image file. If a user can be convinced to view a malicious file,
this vulnerability can be exploited remotely.

DETECTION

The following vendors have confirmed the availability of susceptible
xzgv packages within their respective operating system distributions:
 SuSE
 Debian
 Gentoo
 FreeBSD

WORKAROUND

Only accept image files from trusted sources. Use a different image
viewer program to view untrusted images.

VENDOR RESPONSE

The vulnerability has been addressed in the following patch:

http://rus.members.beeb.net/xzgv-0.8-integer-overflow-fix.diff

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CAN-2004-0994 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

11/05/2004   Initial vendor notification
12/10/2004   Secondary vendor notification
12/10/2004   Initial vendor response
12/13/2004   Coordinated public disclosure

CREDIT

Infamous41md is credited with this discovery.

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LEGAL NOTICES

Copyright © 2004 Verisign, Inc.

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