CVE-2017-12339 in NX-OS
Summary
by MITRE
A vulnerability in the CLI of Cisco NX-OS System Software could allow an authenticated, local attacker to perform a command injection attack. The vulnerability is due to insufficient input validation of command arguments to the CLI parser. An attacker could exploit this vulnerability by injecting crafted command arguments into a vulnerable CLI command. An exploit could allow the attacker to execute arbitrary commands at the user's privilege level. On products that support multiple virtual device contexts (VDCs), this vulnerability could allow the attacker to execute commands at the user's privilege level outside the user's environment. This vulnerability affects the following products running Cisco NX-OS System Software: Multilayer Director Switches, Nexus 2000 Series Fabric Extenders, Nexus 3000 Series Switches, Nexus 5000 Series Switches, Nexus 5500 Platform Switches, Nexus 5600 Platform Switches, Nexus 6000 Series Switches, Nexus 7000 Series Switches, Nexus 7700 Series Switches, Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) mode, Nexus 9000 Series Switches in standalone NX-OS mode, and Nexus 9500 R-Series Line Cards and Fabric Modules. Cisco Bug IDs: CSCve99925, CSCvf15164, CSCvf15167, CSCvf15170, CSCvf15173.
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Analysis
by VulDB Data Team • 01/25/2021
The vulnerability described in CVE-2017-12339 represents a critical command injection flaw within the command line interface of Cisco NX-OS system software, specifically targeting the CLI parser's inadequate input validation mechanisms. This weakness allows authenticated local attackers to manipulate command arguments and inject malicious payloads that execute at the user's privilege level. The vulnerability stems from insufficient sanitization of user inputs passed to CLI commands, creating a pathway for arbitrary code execution that bypasses normal security controls. The flaw affects a broad range of Cisco networking equipment including multilayer directors, various Nexus series switches, and ACI-mode fabric switches, making it particularly concerning for enterprise network infrastructure.
The technical exploitation of this vulnerability occurs through careful crafting of command arguments that are not properly validated by the CLI parser before execution. When an attacker provides malicious input to a vulnerable CLI command, the system fails to properly sanitize the input, allowing the injected commands to be processed and executed with the privileges of the authenticated user. This command injection occurs at the operating system level within the NX-OS environment, potentially enabling attackers to escalate their privileges or access sensitive system resources. The vulnerability specifically impacts the CLI parser component which handles user inputs for various network management functions, making it a fundamental weakness in the system's security architecture. According to CWE classification, this represents a command injection vulnerability (CWE-77) that falls under the broader category of input validation failures.
The operational impact of this vulnerability extends beyond simple privilege escalation, particularly on devices supporting multiple virtual device contexts (VDCs). In environments where VDCs are utilized, attackers can potentially execute commands outside their designated environment, effectively breaking the isolation boundaries between virtual contexts. This cross-context execution capability significantly amplifies the attack surface and could allow an attacker to compromise multiple network segments or services within a single device. The vulnerability affects both standalone NX-OS mode and ACI mode deployments, indicating its prevalence across different Cisco networking deployment models. Organizations running affected Cisco hardware are exposed to potential unauthorized access, data exfiltration, and network disruption through this authenticated local attack vector.
Mitigation strategies for this vulnerability should focus on implementing strict input validation and sanitization within the CLI parser component. Network administrators should ensure immediate deployment of Cisco's security patches and updates addressing this specific bug, as referenced in the Cisco bug IDs CSCve99925 through CSCvf15173. Additional protective measures include implementing least privilege access controls, monitoring CLI usage patterns for suspicious command sequences, and maintaining strict access controls to network management interfaces. The ATT&CK framework categorizes this vulnerability under the T1059.001 technique for command and scripting interpreter, highlighting the need for comprehensive logging and detection of command injection attempts. Organizations should also consider implementing network segmentation and monitoring solutions to detect anomalous CLI behavior that might indicate exploitation attempts. Regular security assessments and vulnerability scanning of network infrastructure should be conducted to identify and remediate similar input validation weaknesses across the entire network ecosystem.