CVE-2021-28501 in EOS
Summary
by MITRE • 01/14/2022
An issue has recently been discovered in Arista EOS where the incorrect use of EOS's AAA API’s by the OpenConfig and TerminAttr agents could result in unrestricted access to the device for local users with nopassword configuration.
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Analysis
by VulDB Data Team • 01/19/2022
The vulnerability identified as CVE-2021-28501 represents a critical security flaw within Arista EOS operating systems that affects network devices running the Arista EOS software. This issue stems from improper implementation of the AAA (Authentication, Authorization, and Accounting) Application Programming Interface within the Arista network operating system. The vulnerability specifically impacts the OpenConfig and TerminAttr agents which are integral components responsible for configuration management and telemetry data collection within Arista devices. When these agents incorrectly utilize the AAA API functions, they create a pathway for unauthorized access that bypasses normal authentication mechanisms.
The technical root cause of this vulnerability lies in how the AAA API is invoked by the OpenConfig and TerminAttr agents during their operational procedures. The flaw manifests when these agents attempt to process configuration changes or access device resources without properly validating user credentials or enforcing standard authentication protocols. This misconfiguration creates a privilege escalation scenario where local users can gain unrestricted access to the device without requiring password authentication. The vulnerability is particularly concerning because it operates at the system level within the EOS kernel, making it difficult to detect through conventional network monitoring approaches.
The operational impact of CVE-2021-28501 extends beyond simple unauthorized access as it fundamentally undermines the security posture of affected Arista devices. Local users with nopassword configuration can potentially execute arbitrary commands, modify device configurations, access sensitive network data, and manipulate telemetry streams. This vulnerability directly violates the principle of least privilege and can enable attackers to establish persistent access points within network infrastructure. The implications are severe for network security as it allows for complete device compromise without the need for external network access or traditional authentication credentials. Organizations relying on Arista EOS devices for core network operations face significant risk of data breaches, service disruption, and potential lateral movement within their network environments.
This vulnerability aligns with CWE-284 (Improper Access Control) and CWE-306 (Missing Authentication for Critical Function) within the CWE taxonomy, representing a clear failure in access control mechanisms and authentication enforcement. From an ATT&CK framework perspective, this issue maps to T1078 (Valid Accounts) and T1566 (Phishing) as it allows for unauthorized access through legitimate system interfaces and could be exploited as part of broader attack chains. The vulnerability also intersects with T1068 (Exploitation for Privilege Escalation) since it provides a mechanism for local users to escalate their privileges without requiring additional attack vectors. Organizations should implement immediate mitigations including updating to patched versions of Arista EOS, reviewing and hardening AAA configurations, and monitoring for unauthorized access attempts. Network segmentation and additional access controls should be deployed to reduce the potential impact of exploitation. Regular security assessments and vulnerability scanning should be conducted to identify similar configuration issues across the network infrastructure.