CVE-2020-3459 in FXOS
Summary
by MITRE • 10/22/2020
A vulnerability in the CLI of Cisco FXOS Software could allow an authenticated, local attacker to inject arbitrary commands that are executed with root privileges. The vulnerability is due to insufficient input validation of commands supplied by the user. An attacker could exploit this vulnerability by authenticating to a device and submitting crafted input to the affected command. A successful exploit could allow the attacker to execute commands on the underlying operating system with root privileges.
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Analysis
by VulDB Data Team • 11/26/2020
The vulnerability identified as CVE-2020-3459 resides within the Command Line Interface of Cisco FXOS Software, representing a critical security flaw that undermines the integrity of authenticated system access controls. This issue affects Cisco FXOS versions prior to 8.3.1.1, where the software fails to properly validate user input submitted through the CLI interface. The vulnerability stems from inadequate sanitization of command inputs, creating a pathway for privilege escalation attacks that can compromise the entire system's security posture.
This vulnerability operates as a command injection flaw that directly violates the principle of least privilege and input validation best practices. The flaw is classified under CWE-77 as a Command Injection vulnerability, where user-supplied data is not properly sanitized before being processed by the system. An authenticated local attacker with access to the device can exploit this weakness by crafting malicious input that bypasses normal command parsing mechanisms. The attack vector requires only local authentication credentials, making it particularly dangerous as it eliminates the need for external network access or complex exploitation techniques.
The operational impact of CVE-2020-3459 is severe and far-reaching, as successful exploitation grants attackers complete root access to the underlying operating system. This privilege escalation allows malicious actors to execute arbitrary code with the highest possible system permissions, potentially enabling them to install backdoors, modify system files, exfiltrate sensitive data, or establish persistent access to the compromised device. The vulnerability affects Cisco's Fabric Services Operating System which manages network infrastructure components, making it a critical target for attackers seeking to compromise network security foundations. The implications extend beyond individual device compromise to potentially affect entire network segments that rely on these services.
From a threat modeling perspective, this vulnerability aligns with ATT&CK technique T1059.001 for Command and Scripting Interpreter, where attackers leverage legitimate system interfaces to execute malicious commands. The attack pattern follows a typical privilege escalation workflow where initial access is gained through legitimate authentication, followed by exploitation of input validation weaknesses to achieve elevated privileges. Organizations should implement immediate mitigations including applying the latest firmware updates from Cisco, which address the input validation flaws in the FXOS CLI. Additionally, network segmentation and access control measures should be strengthened to limit local access points, while monitoring systems should be configured to detect unusual command execution patterns that may indicate exploitation attempts. The vulnerability serves as a reminder of the critical importance of input validation in system interfaces and the potential consequences of inadequate sanitization of user-supplied data in privileged execution contexts.