CVE-2018-0194 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 • 02/08/2021
The vulnerability described in CVE-2018-0194 represents a critical command injection flaw within the Command Line Interface parser of Cisco IOS XE Software, specifically targeting the underlying Linux shell component. This vulnerability manifests as a failure in input sanitization mechanisms that should prevent malicious command arguments from being passed directly to the Linux shell for execution. The flaw exists in the software's CLI processing logic where user-supplied arguments are not properly validated or escaped before being interpreted by the system shell, creating a pathway for arbitrary command execution. Security researchers identified this issue through analysis of the software's command handling procedures, which failed to implement proper parameter sanitization before shell invocation.
The technical exploitation of this vulnerability requires an authenticated local attacker who can submit malicious CLI commands to the affected software system. This attack vector operates under the premise that the attacker already possesses valid credentials to access the device's CLI interface, which significantly reduces the attack surface complexity compared to remote exploitation scenarios. The exploitation process involves crafting specific command arguments that bypass the CLI's normal parsing mechanisms and instead force the system to execute unintended shell commands. This occurs because the software's command processing does not adequately distinguish between legitimate user input and potentially malicious command sequences that could escape the CLI context and directly interact with the underlying Linux shell.
The operational impact of this vulnerability is severe and encompasses complete system compromise with root privileges. Successful exploitation allows attackers to break out of the restricted CLI environment and gain direct access to the underlying Linux shell, where they can execute arbitrary commands with the highest possible privileges. This privilege escalation capability enables attackers to modify system configurations, install malicious software, exfiltrate sensitive data, or establish persistent access points within the network infrastructure. The vulnerability affects the fundamental security model of the affected Cisco IOS XE devices, potentially compromising the integrity and confidentiality of all network services running on the compromised system.
The vulnerability aligns with CWE-78, which describes improper neutralization of special elements used in OS commands, and represents a classic command injection attack pattern. From an ATT&CK framework perspective, this vulnerability maps to techniques involving command and scripting interpreter execution, privilege escalation, and persistence mechanisms. The attack chain typically begins with initial access through legitimate authentication, followed by command injection to escalate privileges, and concludes with the execution of malicious payloads with root-level system access. Organizations should consider this vulnerability as part of a broader attack surface that includes both local and potentially remote exploitation scenarios, particularly when considering the implications of authenticated access to network infrastructure devices.
Mitigation strategies for CVE-2018-0194 should prioritize immediate software patching from Cisco, specifically addressing the identified bug IDs CSCuz03145, CSCuz56419, CSCva31971, and CSCvb09542. Network administrators should implement strict access controls and monitor CLI usage patterns for anomalous command sequences that might indicate exploitation attempts. The implementation of proper input validation and sanitization mechanisms within CLI parsers should be enforced across all network infrastructure devices. Additionally, organizations should conduct comprehensive vulnerability assessments to identify similar command injection vulnerabilities in other network equipment and ensure that all administrative interfaces implement robust authentication and authorization controls. Regular security audits should include verification of command processing logic to prevent similar issues from emerging in future software versions.