CVE-2020-1666 in Junos
Summary
by MITRE • 10/17/2020
The system console configuration option 'log-out-on-disconnect' In Juniper Networks Junos OS Evolved fails to log out an active CLI session when the console cable is disconnected. This could allow a malicious attacker with physical access to the console the ability to resume a previous interactive session and possibly gain administrative privileges. This issue affects all Juniper Networks Junos OS Evolved versions after 18.4R1-EVO, prior to 20.2R1-EVO.
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Analysis
by VulDB Data Team • 11/20/2020
The vulnerability described in CVE-2020-1666 represents a critical security flaw in Juniper Networks Junos OS Evolved operating systems where the console session management mechanism fails to properly terminate active command-line interface sessions upon physical disconnection of the console cable. This issue specifically impacts the 'log-out-on-disconnect' configuration option which is designed to ensure that when a console connection is severed, the associated administrative session should automatically terminate. The flaw exists in all versions of Junos OS Evolved released after 18.4R1-EVO but before 20.2R1-EVO, creating a window of exposure for organizations running these affected systems.
From a technical perspective, this vulnerability manifests as a failure in the session management protocol that governs how the operating system handles console disconnections. When a console cable is physically removed from a device running an affected Junos OS Evolved version, the system should automatically invalidate the active CLI session and require re-authentication upon reconnection. However, the system fails to execute this logout procedure, leaving the session in an active state. This behavior creates a persistent administrative session that can be resumed by anyone with physical access to the console port, effectively bypassing the normal authentication and authorization controls that should protect administrative access to network infrastructure devices. The vulnerability directly relates to CWE-613, which addresses inadequate session management and the persistence of session tokens after expected termination events.
The operational impact of this vulnerability is particularly severe given the physical access requirement for exploitation, which aligns with ATT&CK technique T1018 for Valid Accounts and T1087 for Account Discovery. An attacker with physical access to a network device could exploit this vulnerability to gain continued administrative access without needing to know passwords or credentials. This creates a significant risk for organizations where physical security controls may be insufficient or where unauthorized personnel have access to network equipment. The vulnerability essentially creates a backdoor access method that bypasses traditional authentication mechanisms, allowing persistent access to administrative functions. Organizations using affected Junos OS Evolved versions face potential compromise of their network infrastructure, particularly in environments where physical security is not strictly enforced or where devices are located in accessible areas.
Mitigation strategies for this vulnerability should focus on immediate remediation through software updates to versions 20.2R1-EVO or later where the issue has been addressed. Organizations should also implement additional physical security controls including cable locks, secure device enclosures, and restricted access to network equipment locations. Network administrators should consider implementing additional monitoring and alerting mechanisms to detect unauthorized console access attempts and session resumption activities. The configuration option 'log-out-on-disconnect' should be verified to ensure proper operation in all environments, and organizations should conduct regular security assessments to identify potential unauthorized access points. Additionally, implementing strong physical security controls such as access logs, surveillance monitoring, and restricted personnel access to network equipment areas can help mitigate the risk associated with this vulnerability. This issue underscores the importance of proper session management in network infrastructure devices and the critical need for comprehensive security controls that address both logical and physical access points to network equipment.