CVE-2017-7905 in Multilin Protection Relay
Summary
by MITRE
A Weak Cryptography for Passwords issue was discovered in General Electric (GE) Multilin SR 750 Feeder Protection Relay, firmware versions prior to Version 7.47; SR 760 Feeder Protection Relay, firmware versions prior to Version 7.47; SR 469 Motor Protection Relay, firmware versions prior to Version 5.23; SR 489 Generator Protection Relay, firmware versions prior to Version 4.06; SR 745 Transformer Protection Relay, firmware versions prior to Version 5.23; SR 369 Motor Protection Relay, all firmware versions; Multilin Universal Relay, firmware Version 6.0 and prior versions; and Multilin URplus (D90, C90, B95), all versions. Ciphertext versions of user passwords were created with a non-random initialization vector leaving them susceptible to dictionary attacks. Ciphertext of user passwords can be obtained from the front LCD panel of affected products and through issued Modbus commands.
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Analysis
by VulDB Data Team • 12/30/2020
The vulnerability identified as CVE-2017-7905 represents a critical weakness in the cryptographic implementation of several General Electric Multilin protection relays, specifically affecting firmware versions prior to designated updates. This weakness stems from the implementation of weak cryptography for password storage, creating a significant security risk for industrial control systems. The affected devices include various feeder, motor, generator, and transformer protection relays across multiple product lines, indicating a widespread issue that impacts critical infrastructure protection mechanisms. The vulnerability is classified under CWE-327, which specifically addresses the use of weak cryptographic algorithms and improper implementation of cryptographic functions. These protection relays are commonly deployed in power generation, transmission, and distribution systems where unauthorized access could lead to severe operational disruptions and safety hazards.
The technical flaw manifests in the use of a non-random initialization vector during the encryption process of user passwords, which fundamentally undermines the security of the cryptographic implementation. When passwords are encrypted using a fixed or predictable initialization vector, the resulting ciphertext becomes vulnerable to dictionary attacks and pattern analysis techniques. The initialization vector should be random and unique for each encryption operation to ensure that identical plaintext passwords produce different ciphertext outputs. However, in this implementation, the predictable initialization vector allows attackers to analyze the encrypted password data and potentially reverse-engineer the original passwords through systematic attacks. This weakness is particularly concerning because the encrypted passwords can be directly obtained from the front LCD panel displays of these devices, providing attackers with readily accessible ciphertext without requiring complex network infiltration techniques.
The operational impact of this vulnerability extends beyond simple credential compromise, as these protection relays are critical components in industrial control systems that manage power generation and distribution infrastructure. An attacker who successfully exploits this weakness could gain unauthorized access to system configuration and operational controls, potentially leading to service disruption, equipment damage, or safety hazards. The vulnerability affects multiple relay types including SR 750, SR 760, SR 469, SR 489, SR 745, SR 369, Multilin Universal Relay, and URplus series devices, indicating that this weakness is embedded in core firmware implementations across different protection relay architectures. The ability to obtain ciphertext through Modbus commands further expands the attack surface, as these protocols are commonly used for communication between industrial devices and supervisory control systems. This vulnerability aligns with ATT&CK technique T1210, which involves exploitation of remote services for credential access, and represents a significant risk to industrial cybersecurity posture.
Organizations should implement immediate mitigation strategies including firmware updates to the latest versions that address the weak cryptography implementation, along with network segmentation to limit access to these devices. The affected systems require comprehensive vulnerability assessments to identify all instances of the vulnerable firmware versions and ensure proper patch management procedures are in place. Additionally, network monitoring should be enhanced to detect unauthorized Modbus communication attempts that could be used to extract password ciphertext. Security teams should consider implementing additional authentication mechanisms such as two-factor authentication for these critical devices, as the current implementation relies solely on password-based access control. The vulnerability demonstrates the importance of proper cryptographic implementation in industrial control systems and highlights the need for rigorous security testing of embedded firmware in critical infrastructure devices. Regular security audits and continuous monitoring of industrial network traffic are essential to prevent exploitation of similar weaknesses in other embedded systems that may be susceptible to the same class of cryptographic vulnerabilities.