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KLCERT-20-020: Moxa NPort IA5000A Series. Using the Telnet service

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KL-IDS KLCERT-20-020
CVE-IDS CVE-2020-27184
Publication date 2021.05.11
Researcher Alexander Nochvay, Kaspersky ICS CERT
Description The NPort devices use Telnet as one of the network device management services. Telnet does not support the encryption of client-server communications, making it vulnerable to Man-in-the-Middle attacks.
Impact An attacker could read all data transferred between the client and the device if the communication is carried out over the Telnet protocol, including authentication credentials, device configuration data, other sensitive data, version of the device, etc.
Severity
CVSS v3 Base Score: 5.3
Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
Exploitability Remotely exploitable: network access to port 23/TCP is required
Difficulty High skill level to exploit: an attacker must perform Man-in-the-Middle attack
Privilege required No privileges required
User interaction User interaction required: it requires to communicate over Telnet by user
Existence of exploit Unknown
Affected products
Affected products NPort IA5150A-IEX
NPort IA5150A-T-IEX
NPort IA5150A-T
NPort IA5150A
NPort IA5150AI-IEX
NPort IA5150AI-T-IE
NPort IA5150AI-T
NPort IA5150AI
NPort IA5250A-IEX
NPort IA5250A-T-IEX
NPort IA5250A-T
NPort IA5250A
NPort IA5250AI-IEX
NPort IA5250AI-T-IE
NPort IA5250AI-T
NPort IA5250AI
NPort IA5450A-T
NPort IA5450A
NPort IA5450AI-T
NPort IA5450AI
Mitigation
Vendor mitigation

Moxa products can disable the Telnet service to mitigate this risk. Please refer to the Console Settings section in the user manual for more details. Firmware version 1.5 or higher will disable Telnet by default on the NPort IA5150A/IA5250A Series. Firmware version 2.0 or higher will disable Telnet by default on the NPort IA5450A Series.

Link to Moxa’s advisory: https://www.moxa.com/en/support/product-support/security-advisory/nport-ia5000a-serial-device-servers-vulnerabilities

KL mitigation

Set up a border firewall (or a similar network traffic control solution) passing traffic into the device’s network segment to allow traffic to port 23/TCP from authorized parties only.

Disable Telnet service on NPort device if it is possible in your environments

Firewall. Configure the firewall to restrict access to the industrial network in such a way that only essential communications from authorized sources are allowed. This will help reduce the attack surface. Make sure that the firewall restrictions do not affect core business workflows.

VPN. Use virtual private networks (VPN) to secure remote access to the industrial network. A VPN encrypts network traffic between VPN clients and the VPN server, as well as providing secure authorized access to local resources on the company’s internal network. Traffic encryption protects against traffic eavesdropping attacks, including man-in-the-middle (MitM) and other types of traffic analysis attacks.

Network monitoring. Implement a network intrusion detection solution (NIDS). A comprehensive IDS solution is capable of detecting unusual network connections and abnormal traffic sent to the device, providing timely information about various suspicious activities and sufficiently reducing the attacker’s chances of successful exploitation.

Network segmentation. Compartmentalize your network: implement network segmentation and strict access control for each segment to provide more comprehensive and effective protection against a wide range of threats. Proper network segmentation prevents attackers from reaching critical assets in the event of a network breach

Timeline 14.08.2020 – Vulnerability reported
24.08.2020 – Moxa confirmed the vulnerability
28.04.2021 – Moxa published the advisory