CVE-2021-28507 in EOS
Summary
by MITRE • 01/14/2022
An issue has recently been discovered in Arista EOS where, under certain conditions, the service ACL configured for OpenConfig gNOI and OpenConfig RESTCONF might be bypassed, which results in the denied requests being forwarded to the agent.
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Analysis
by VulDB Data Team • 01/19/2022
The vulnerability identified as CVE-2021-28507 represents a significant security flaw in Arista Enterprise Operating System (EOS) that affects the implementation of access control mechanisms for critical network management interfaces. This issue specifically impacts the OpenConfig gNOI and OpenConfig RESTCONF services, which are essential components for remote network device management and configuration. The flaw exists within the service Access Control List (ACL) implementation that is supposed to enforce security policies and restrict unauthorized access to these management interfaces.
The technical nature of this vulnerability stems from a failure in the ACL processing logic within Arista EOS where certain conditions can cause the system to bypass the configured access control rules. When these conditions are met, requests that should be denied based on the ACL configuration are incorrectly forwarded to the underlying agent processes, effectively allowing unauthorized access to network management functions. This bypass mechanism operates at the network protocol level where the system fails to properly evaluate the access control policies before routing management requests to the appropriate service handlers.
The operational impact of this vulnerability is substantial as it creates a potential attack vector for malicious actors to gain unauthorized access to network devices through the gNOI and RESTCONF management interfaces. Network administrators who rely on these services for device management and configuration are at risk of having their devices compromised, potentially leading to unauthorized configuration changes, data exfiltration, or disruption of network services. The vulnerability is particularly concerning because it affects the fundamental security controls that protect management interfaces from unauthorized access, making it a critical issue for network security posture.
This vulnerability aligns with CWE-284, which describes improper access control issues in software systems, and represents a failure in implementing proper authorization checks for network management services. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and lateral movement through network device management interfaces, potentially enabling adversaries to establish persistent access to network infrastructure. The bypass mechanism creates a pathway for attackers to perform reconnaissance, configuration changes, and potentially execute malicious commands on affected network devices.
Organizations should immediately implement mitigations including updating to patched versions of Arista EOS where available, implementing additional network segmentation controls, and monitoring for unauthorized access attempts to management interfaces. Network administrators should also review and strengthen their access control policies, implement multi-factor authentication for management access, and conduct regular security assessments of their network device configurations. The vulnerability underscores the importance of robust access control implementation in network management systems and highlights the critical need for continuous security testing and validation of security controls in enterprise network infrastructure.