CVE-2017-6650 in NX-OS
Summary
by MITRE
A vulnerability in the Telnet CLI command of Cisco NX-OS System Software 7.1 through 7.3 running on Cisco Nexus 5000 Series Switches could allow an authenticated, local attacker to perform a command injection attack. The vulnerability is due to insufficient input validation of command arguments. An attacker could exploit this vulnerability by injecting crafted command arguments into the Telnet CLI command. An exploit could allow the attacker to read or write arbitrary files at the user's privilege level outside of the user's path. Cisco Bug IDs: CSCvb86771.
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Analysis
by VulDB Data Team • 12/25/2020
The vulnerability identified as CVE-2017-6650 resides within the Telnet CLI command implementation of Cisco NX-OS System Software versions 7.1 through 7.3 running on Cisco Nexus 5000 Series Switches. This represents a critical security flaw that directly impacts the integrity and confidentiality of network infrastructure devices. The vulnerability stems from inadequate input validation mechanisms that fail to properly sanitize command arguments passed to the Telnet CLI functionality, creating an exploitable condition that can be leveraged by authenticated local attackers.
This command injection vulnerability operates through the manipulation of command arguments within the Telnet CLI interface, allowing an authenticated attacker with local access to the switch to inject malicious commands that execute with the privileges of the current user session. The flaw specifically affects the command processing logic where user-supplied arguments are not adequately validated or escaped before being processed, enabling arbitrary command execution within the constraints of the user's privilege level. The vulnerability permits attackers to perform file operations outside of the normal user path restrictions, potentially allowing unauthorized access to sensitive system files or the ability to modify system configurations.
The operational impact of this vulnerability extends beyond simple privilege escalation as it provides attackers with the capability to read or write arbitrary files at the user's privilege level, potentially compromising system integrity and confidentiality. Attackers could leverage this vulnerability to access sensitive configuration data, modify system files, or potentially establish persistent access to the network switch. The local authentication requirement means that the attacker must already have legitimate access to the device, but this does not mitigate the severity of the impact given that network administrators typically grant administrative privileges to authorized personnel who may be compromised. The vulnerability affects the core network infrastructure, potentially disrupting network operations and providing attackers with a foothold for further network exploration and lateral movement.
The technical exploitation of this vulnerability aligns with CWE-77 and CWE-94, which respectively address command injection and improper restriction of operations within a recognized blacklist. The flaw represents a classic command injection attack vector where user input is directly incorporated into system commands without proper sanitization. From an adversarial perspective, this vulnerability maps to ATT&CK technique T1059.001 for command and scripting interpreter, specifically the use of command shells. The vulnerability's impact is amplified by the fact that it operates at the user privilege level rather than requiring root or administrative privileges, making it particularly concerning for environments where multiple users have access to network devices. Organizations should implement immediate mitigations including applying Cisco's recommended security patches, implementing strict input validation controls, and monitoring for unauthorized access attempts. Network segmentation and privilege management controls should be enhanced to limit the potential impact of such vulnerabilities, while regular security assessments should be conducted to identify similar input validation weaknesses across network infrastructure components.