AWStats Remote Command Execution Vulnerability

iDEFENSE Security Advisory 01.17.05
www.idefense.com/application/poi/display?id=185&type=vulnerabilities
January 17, 2005

I. BACKGROUND

AWStats is a free tool that generates advanced web, ftp or mail server
statistics, graphically. More information about AWStats is available
from:

    http://awstats.sourceforge.net

II. DESCRIPTION

Remote exploitation of an input validation vulnerability in AWStats
allows attackers to execute arbitrary commands under the privileges of
the web server.

The problem specifically exists when the application is running as a
CGI script on a web server. The "configdir" parameter contains
unfiltered user-supplied data that is utilized in a call to the Perl
routine open() as can be seen here on line 1082 of awstats.pl:

    if (open(CONFIG,"$searchdir$PROG.$SiteConfig.conf"))

The "searchdir" variables hold the value of the parameter provided by
the attacker from "configdir." An attacker can cause arbitrary commands
to be executed by prefixing them with the "|" character.

III. ANALYSIS

Successful exploitation allows remote attackers to execute arbitrary
commands under the privileges of the web server. This can lead to
further compromise as it provides remote attackers with local access.

IV. DETECTION

iDEFENSE has confirmed that AWStats version 6.1 is vulnerable.
It is suspected that earlier versions are also vulnerable.

V. WORKAROUND

Add a filter around the "configdir" parameter by replacing the following
line:

    if ($QueryString =~ /configdir=([^&]+)/i)
    {
        $DirConfig=&DecodeEncodedString("$1");
    }

With:

    if ($QueryString =~ /configdir=([^&]+)/i)
    {
        $DirConfig=&DecodeEncodedString("$1");
        $DirConfig=~tr/a-z0-9_\-\/\./a-z0-9_\-\/\./cd;
    } 

VI. VENDOR RESPONSE

This vulnerability is addressed in AWStats 6.3, available for download
at:

   http://awstats.sourceforge.net/#DOWNLOAD

VII. CVE INFORMATION

A Mitre Corp. Common Vulnerabilities and Exposures (CVE) number has not
been assigned yet.

VIII. DISCLOSURE TIMELINE

10/21/2004  Initial vendor notification
01/02/2005  Initial vendor response
01/17/2005  Public disclosure

IX. CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

Get paid for vulnerability research
http://www.idefense.com/poi/teams/vcp.jsp

X. LEGAL NOTICES

Copyright (c) 2005 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.