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. 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. _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.netsys.com/full-disclosure-charter.html