CVE-2018-0176 in IOS XE
Summary
by MITRE
Multiple vulnerabilities in the CLI parser of Cisco IOS XE Software could allow an authenticated, local attacker to gain access to the underlying Linux shell of an affected device and execute arbitrary commands with root privileges on the device. The vulnerabilities are due to the affected software improperly sanitizing command arguments to prevent access to internal data structures on a device. An attacker who has user EXEC mode (privilege level 1) access to an affected device could exploit these vulnerabilities on the device by executing CLI commands that contain crafted arguments. A successful exploit could allow the attacker to gain access to the underlying Linux shell of the affected device and execute arbitrary commands with root privileges on the device. Cisco Bug IDs: CSCtw85441, CSCus42252, CSCuv95370.
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Analysis
by VulDB Data Team • 02/06/2021
The vulnerability identified as CVE-2018-0176 represents a critical command injection flaw within the Command Line Interface parser of Cisco IOS XE Software, specifically affecting devices running this operating system. This vulnerability resides in the software's improper sanitization of command arguments, creating a pathway for authenticated local attackers to escalate their privileges and gain root access to the underlying Linux shell. The flaw is particularly concerning because it allows an attacker with minimal privileges to exploit the system and execute arbitrary code with the highest level of system permissions, effectively compromising the entire device.
The technical implementation of this vulnerability stems from the software's inadequate validation and sanitization of user inputs passed through CLI commands. When an authenticated user with user EXEC mode privileges (privilege level 1) submits crafted command arguments, the system fails to properly filter or escape these inputs, allowing malicious payloads to traverse the command parser and access internal data structures. This improper input handling creates a direct attack vector that bypasses normal security boundaries, enabling privilege escalation from user level to root access. The vulnerability manifests through specific Cisco Bug IDs CSCtw85441, CSCus42252, and CSCuv95370, which document various aspects of the command injection mechanism that enables this exploitation path.
The operational impact of CVE-2018-0176 is severe and multifaceted, as it provides attackers with complete control over affected devices. Once exploited, attackers can execute arbitrary commands with root privileges, potentially leading to data exfiltration, system compromise, network reconnaissance, and further lateral movement within the network infrastructure. The vulnerability affects a wide range of Cisco IOS XE Software versions, making it particularly dangerous as it could impact numerous network devices across different organizations. The local nature of the attack means that an attacker only needs access to the device's CLI to exploit this vulnerability, which could occur through legitimate administrative access or through compromised credentials.
From a cybersecurity perspective, this vulnerability aligns with CWE-77 and CWE-78 categories, representing command injection flaws that allow arbitrary code execution through improper input validation. The attack pattern follows typical privilege escalation techniques documented in MITRE ATT&CK framework under T1068 (Local Privilege Escalation) and T1059 (Command and Scripting Interpreter) tactics. Organizations affected by this vulnerability face significant risk of unauthorized access to critical network infrastructure, potentially leading to service disruption, data breaches, and compliance violations. The vulnerability's exploitation requires minimal skill level and can be automated, making it particularly dangerous for widespread compromise.
Mitigation strategies for CVE-2018-0176 primarily focus on immediate software updates and patches provided by Cisco to address the underlying command parsing issues. Organizations should prioritize patching affected devices with the latest IOS XE software releases that contain fixes for the identified vulnerabilities. Network segmentation and access controls should be implemented to limit user EXEC mode access to only authorized personnel, while monitoring systems should be deployed to detect suspicious CLI command patterns. Additionally, implementing strong authentication mechanisms, regular security audits, and privileged access management solutions can help reduce the attack surface and prevent unauthorized access to affected devices. Regular vulnerability assessments and security awareness training for network administrators are essential components of a comprehensive defense strategy against this type of privilege escalation attack.