CVE-2017-7928 in SEL-3620
Summary
by MITRE
An Improper Access Control issue was discovered in Schweitzer Engineering Laboratories (SEL) SEL-3620 and SEL-3622 Security Gateway Versions R202 and, R203, R203-V1, R203-V2 and, R204, R204-V1. The device does not properly enforce access control while configured for NAT port forwarding, which may allow for unauthorized communications to downstream devices.
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Analysis
by VulDB Data Team • 11/04/2019
The CVE-2017-7928 vulnerability represents a critical improper access control flaw within Schweitzer Engineering Laboratories SEL-3620 and SEL-3622 Security Gateway devices. This vulnerability specifically affects firmware versions R202 through R204-V1, creating a significant security gap in industrial control systems where proper network segmentation and access control are paramount. The issue manifests when devices are configured for NAT port forwarding operations, a common configuration in industrial environments where network address translation is required to manage communications between different network segments. The vulnerability stems from insufficient validation of access permissions during the NAT port forwarding process, allowing malicious actors to potentially bypass intended network security controls.
The technical flaw in this vulnerability aligns with CWE-284, which describes improper access control mechanisms where systems fail to properly enforce access restrictions. When the SEL security gateways are configured for NAT port forwarding, the devices should maintain strict control over which external communications can reach internal network devices. However, the vulnerability allows unauthorized external entities to establish connections to downstream devices that should normally be protected from direct external access. This occurs because the access control enforcement mechanisms fail to properly validate source addresses, destination ports, or other critical connection parameters during the NAT translation process. The flaw essentially creates a backdoor pathway through which unauthorized communications can traverse the network boundary, potentially compromising the integrity and availability of connected industrial control systems.
From an operational impact perspective, this vulnerability presents severe risks to industrial control system security, particularly in critical infrastructure environments where SEL devices are commonly deployed. The vulnerability could enable attackers to gain unauthorized access to downstream devices such as programmable logic controllers, remote terminal units, or other industrial network components that are typically isolated from external network access. Attackers could potentially exploit this weakness to inject malicious commands, monitor network traffic, or disrupt operational processes that depend on these industrial control systems. The impact extends beyond simple unauthorized access as it undermines the fundamental security architecture of the network, potentially allowing for lateral movement within the industrial network and escalation of privileges. This vulnerability particularly affects environments where network segmentation is critical for maintaining operational technology security, such as power generation, water treatment, and manufacturing facilities.
Organizations should implement immediate mitigations including firmware updates to versions that address the access control flaw, network segmentation to isolate affected devices, and monitoring of network traffic for suspicious NAT port forwarding activities. The vulnerability also highlights the importance of proper security configuration management in industrial environments, where devices should be configured to minimize unnecessary services and access points. Security professionals should consider implementing network access control lists, intrusion detection systems, and regular security assessments to identify similar configuration weaknesses. The issue also emphasizes the need for robust security testing during the deployment of industrial security devices, particularly those that handle network address translation and port forwarding functions. Organizations should follow the ATT&CK framework's network infiltration techniques when planning security controls, as this vulnerability could enable adversaries to establish persistent access through the compromised NAT functionality. Proper security awareness training for industrial control system operators is also essential to recognize potential signs of exploitation attempts targeting such network configuration vulnerabilities.