Multiple Vendor xzgv PRF Parsing Integer Overflow Vulnerability

iDEFENSE Security Advisory 12.13.04
http://www.idefense.com/application/poi/display?type=vulnerabilities
December 13, 2004

I. 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. 

II. 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.

III. 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.

IV. DETECTION

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

V. WORKAROUND

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

VI. VENDOR RESPONSE

The vulnerability has been addressed in the following patch:

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

VII. 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.

VIII. 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

IX. CREDIT

Infamous41md is credited with this discovery.

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X. LEGAL NOTICES

Copyright (c) 2004 iDEFENSE, Inc.

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Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on,
this information.