CVE-2018-0193 in IOS XE
Summary
by MITRE
Multiple vulnerabilities in the CLI parser of Cisco IOS XE Software could allow an authenticated, local attacker to inject arbitrary commands into the CLI of the affected software, which could allow the attacker to gain access to the underlying Linux shell of an affected device and execute commands with root privileges on the device. The vulnerabilities exist because the affected software does not sufficiently sanitize command arguments before passing commands to the Linux shell for execution. An attacker could exploit these vulnerabilities by submitting a malicious CLI command to the affected software. A successful exploit could allow the attacker to break from the CLI of the affected software, which could allow the attacker to gain access to the underlying Linux shell on an affected device and execute arbitrary commands with root privileges on the device. Cisco Bug IDs: CSCuz03145, CSCuz56419, CSCva31971, CSCvb09542.
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Analysis
by VulDB Data Team • 01/17/2020
The vulnerability described in CVE-2018-0193 represents a critical command injection flaw within the Command Line Interface parser of Cisco IOS XE Software, specifically targeting the underlying Linux shell execution mechanism. This vulnerability stems from inadequate input sanitization practices within the software's command processing pipeline, creating a pathway for authenticated local attackers to escalate privileges and execute arbitrary code with root-level permissions. The flaw affects multiple Cisco IOS XE versions and manifests when the system fails to properly validate and sanitize command arguments before forwarding them to the Linux shell for execution, creating a direct injection vector that bypasses normal security boundaries.
The technical exploitation of this vulnerability requires an authenticated local attacker who can submit malicious CLI commands to the affected software, leveraging the insufficient sanitization to break out of the normal CLI environment and gain access to the underlying Linux shell. This represents a classic command injection vulnerability where user-supplied input is directly concatenated into shell commands without proper validation or escaping mechanisms. The vulnerability is categorized under CWE-78 as "Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')", which aligns with the observed behavior of passing unvalidated arguments directly to the Linux shell. The attack vector operates through the CLI parser's failure to implement proper input filtering, allowing attackers to inject shell metacharacters and commands that execute with elevated privileges.
From an operational perspective, the impact of this vulnerability extends beyond simple privilege escalation to provide full system compromise capabilities for authenticated attackers. The ability to execute commands with root privileges on the underlying Linux system creates a complete compromise of the device's security posture, potentially enabling attackers to modify system configurations, install backdoors, exfiltrate data, or use the compromised device as a pivot point for further attacks within the network. This vulnerability directly maps to ATT&CK technique T1059.001 for Command and Scripting Interpreter, specifically targeting the execution of commands through the Linux shell. The compromise of the underlying operating system provides attackers with access to system-level resources, including file systems, network interfaces, and potentially other connected systems, making this a particularly dangerous vulnerability for network infrastructure devices.
The mitigation strategies for CVE-2018-0193 primarily focus on implementing proper input validation and sanitization measures within the CLI parser component of Cisco IOS XE Software. Organizations should apply the relevant Cisco security patches and updates that address the command injection flaw by implementing proper escaping of special characters and validation of command arguments before shell execution. Network segmentation and least privilege principles should be enforced to limit the potential impact of successful exploitation, while monitoring solutions should be deployed to detect anomalous CLI command patterns that might indicate exploitation attempts. Additionally, regular security audits of CLI configurations and privilege assignments should be conducted to ensure that only authorized users have access to potentially dangerous commands. The vulnerability highlights the critical importance of input validation in security-critical components and demonstrates how insufficient sanitization can create complete system compromise scenarios, emphasizing the need for robust security practices throughout the software development lifecycle.