CVE-2020-3166 in FXOS
Summary
by MITRE
A vulnerability in the CLI of Cisco FXOS Software could allow an authenticated, local attacker to read or write arbitrary files on the underlying operating system (OS). The vulnerability is due to insufficient input validation. An attacker could exploit this vulnerability by including crafted arguments to a specific CLI command. A successful exploit could allow the attacker to read or write to arbitrary files on the underlying OS.
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Analysis
by VulDB Data Team • 04/06/2024
The vulnerability identified as CVE-2020-3166 resides within the Command Line Interface of Cisco FXOS Software, representing a critical security flaw that undermines the integrity of the system's access controls. This issue affects Cisco's Fabric eXtension Operating System which serves as the foundational software for their data center networking solutions. The vulnerability stems from inadequate input validation mechanisms within the CLI parser, creating a pathway for malicious actors to bypass normal security boundaries. The flaw specifically manifests when the system processes command line arguments without proper sanitization, allowing crafted inputs to be interpreted as legitimate system commands. This weakness enables an authenticated local attacker to escalate privileges beyond normal operational boundaries and gain unauthorized access to the underlying operating system's file system.
The technical exploitation of this vulnerability occurs through the manipulation of specific CLI commands that accept user-supplied arguments. When an attacker crafts malicious input parameters and passes them to the vulnerable command, the insufficient validation allows these inputs to be interpreted as direct file system operations. The vulnerability can be leveraged to perform arbitrary read and write operations on the underlying OS, potentially enabling attackers to access sensitive configuration files, system binaries, or other critical data stores. This type of flaw falls under CWE-20, which specifically addresses "Improper Input Validation" and represents a fundamental security weakness in the software's defensive mechanisms. The attack vector requires local authentication, meaning an attacker must first establish legitimate credentials to the system before attempting exploitation, but this initial requirement does not mitigate the severity of potential impact once access is obtained.
The operational impact of CVE-2020-3166 extends beyond simple file access violations, as it provides a potential foothold for more sophisticated attacks within the network infrastructure. An attacker who successfully exploits this vulnerability could modify system files, inject malicious code, or exfiltrate confidential information from the device. The implications are particularly severe in data center environments where Cisco FXOS systems serve as core networking components, as this vulnerability could enable attackers to compromise the entire network fabric. From an adversary perspective, this vulnerability aligns with ATT&CK technique T1059.001 for Command and Scripting Interpreter, specifically through the use of command-line interfaces to execute malicious operations. The ability to perform arbitrary file operations also supports techniques such as T1078 for valid accounts and T1566 for social engineering, as attackers could manipulate system files to maintain persistence or conduct further reconnaissance. The vulnerability essentially provides a bridge between the authenticated user context and system-level file manipulation capabilities.
Mitigation strategies for CVE-2020-3166 should focus on both immediate patching and operational security enhancements. Cisco has released software updates that address the input validation deficiencies in the affected FXOS versions, and organizations should prioritize applying these patches to eliminate the vulnerability. In environments where patching cannot be immediately deployed, administrators should implement additional controls such as restricting local access to the CLI, monitoring command line usage patterns, and implementing strict access controls for system accounts. Network segmentation and privilege separation measures can help limit the potential impact of successful exploitation attempts. Security monitoring should include detection of unusual file access patterns and command execution sequences that might indicate exploitation attempts. Additionally, organizations should consider implementing privileged access management solutions that can restrict the ability to execute potentially dangerous CLI commands. The vulnerability demonstrates the importance of robust input validation practices and highlights the need for comprehensive security testing of CLI interfaces, particularly in systems where local administrative access is required for operational tasks.