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ESB-2005.0613 -- iDEFENSE Security Advisory 08.09.05 -- AWStats ShowInfoURL Remote Command Execution

Date: 10 August 2005
References: ESB-2005.0910  

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             AUSCERT External Security Bulletin Redistribution

           ESB-2005.0613 -- iDEFENSE Security Advisory 08.09.05
               AWStats ShowInfoURL Remote Command Execution
                              10 August 2005

===========================================================================

        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           AWStats 6.3 and prior
Publisher:         iDEFENSE
Operating System:  UNIX variants
                   Windows
Impact:            Execute Arbitrary Code/Commands
Access:            Remote/Unauthenticated
CVE Names:         CAN-2005-1527 CAN-2005-0436

Original Bulletin: http://www.idefense.com/application/poi/display?id=290

Comment: AWStats vulnerabilities have been actively exploited in the past to
         compromise and deface large numbers of web servers [1][2].  Given the
         ease of exploitation and potential for worm-like behaviour, AusCERT
         recommends following the mitigation steps in this advisory as soon as
         possible.
         
         References:
         
         [1] https://www.auscert.org.au/4943
         [2] https://www.auscert.org.au/4807

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AWStats ShowInfoURL Remote Command Execution Vulnerability 

iDEFENSE Security Advisory 08.09.05
www.idefense.com/application/poi/display?id=290&type=vulnerabilities
August 09, 2005

I. BACKGROUND

AWStats is a free tool that generates web, streaming, ftp or mail 
server statistics, graphically. It can analyze log files from all major 
server tools like Apache log files (NCSA combined/XLF/ELF log format or 
common/CLF log format), WebStar, IIS (W3C log format) and other web, 
proxy, wap, streaming servers, mail servers and some ftp servers. More 
information is available at the vendor's website:
     
     http://awstats.sourceforge.net

II. DESCRIPTION

Remote exploitation of an input validation vulnerability in AWStats 
allows remote attackers to execute arbitrary commands.

AWStats is a logfile analysis tool that generates reports for ftp, mail 
and web traffic. The problem specifically exists because of 
insufficient input filtering before passing user-supplied data to an 
eval() function. As part of the statistics reporting function, AWStats 
displays information about the most common referrer values that caused 
users to visit the website. The referrer data is used without proper 
sanitation in an eval() statement, resulting in the execution of 
arbitrary perl code.

Shown as follows, the $url parameter contains unfiltered user-supplied 
data that is used in a call to the Perl routine eval() on lines 4841 
and 4842 of awstats.pl (version 6.4):

     my $function="ShowInfoURL_$pluginname('$url')";
     eval("$function");

The malicious referrer value will be included in the referrer 
statistics portion of the AWStats report after AWStats has been run to 
generate a new report including the tainted data. Once a user visits 
the referrer statistics page, the injected perl code will execute with 
permissions of the web service.

III. ANALYSIS

Successful exploitation results in the execution of arbitrary commands 
with permissions of the web service. Exploitation will not occur until 
the stats page has been regenerated with the tainted referrer values 
from the http access log. Note that AWStats is only vulnerable in 
situations where at least one URLPlugin is enabled.

AWStats is a very commonly used web statistics reporting package. Since 
this attack does not require special privileges, it is recommended that 
users update AWStats to the latest available package.

IV. DETECTION

iDEFENSE Labs has confirmed the existence of this vulnerability in 
AWStats 6.3. All earlier versions are suspected vulnerable. AWStats 6.4 
has been released since the initial research on this vulnerability. 
AWStats 6.4 has replaced all eval() statements, and has mitigated the 
exposure to this vulnerability.

V. WORKAROUND

As a workaround solution, disable all URLPlugins in the AWStats
configuration.

VI. VENDOR RESPONSE

This vulnerability has been addressed with the release of AWStats 6.4.

Updated software packages are available from:
  	
   AWStats 6.4: http://awstats.sourceforge.net/#DOWNLOAD 

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CAN-2005-1527 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org), which standardizes names for
security problems. It should be noted that this is similar to but
different from CAN-2005-0436.

VIII. DISCLOSURE TIMELINE

05/12/2005  Initial vendor notification
08/09/2005  Public disclosure

IX. CREDIT

Peter Vreugdenhil (security[at]petervreugdenhil[dot]nl) is credited with
this discovery.

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

Free tools, research and upcoming events
http://labs.idefense.com

X. LEGAL NOTICES

Copyright (c) 2005 iDEFENSE, Inc.

Permission is granted for the redistribution of this alert
electronically. It may not be edited in any way without the express
written consent of iDEFENSE. If you wish to reprint the whole or any
part of this alert in any other medium other than electronically, please
email customerservice@idefense.com for permission.

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.



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If you believe that your computer system has been compromised or attacked in 
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Incident Reporting Form at:

        http://www.auscert.org.au/render.html?it=3192

===========================================================================
Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072

Internet Email: auscert@auscert.org.au
Facsimile:      (07) 3365 7031
Telephone:      (07) 3365 4417 (International: +61 7 3365 4417)
                AusCERT personnel answer during Queensland business hours
                which are GMT+10:00 (AEST).
                On call after hours for member emergencies only.
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