CVE-2018-0183 in IOS XE
Summary
by MITRE
A vulnerability 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 vulnerability is due to the affected software improperly sanitizing command arguments to prevent access to internal data structures on a device. An attacker who has privileged EXEC mode (privilege level 15) access to an affected device could exploit this vulnerability 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: CSCuv91356.
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Analysis
by VulDB Data Team • 01/17/2020
The vulnerability described in CVE-2018-0183 represents a critical privilege escalation flaw within Cisco IOS XE Software that fundamentally compromises the security posture of affected network devices. This vulnerability exists in the command line interface parser implementation where insufficient input sanitization allows maliciously crafted command arguments to bypass normal security controls. The flaw specifically targets the way the software processes user inputs within the CLI environment, creating a pathway for authenticated attackers to escape the restricted command interface and access the underlying Linux shell that powers the device's operating system. The vulnerability is particularly dangerous because it requires only privileged EXEC mode access, which is typically limited to authorized administrators with privilege level 15, making it accessible to insiders or attackers who have already gained administrative credentials.
The technical exploitation of this vulnerability leverages the improper sanitization of command arguments to manipulate the CLI parser into executing unintended operations that expose internal system structures. When an authenticated user with privilege level 15 executes specifically crafted CLI commands containing malicious arguments, the vulnerable parser fails to properly validate or sanitize these inputs before processing them. This failure allows the attacker to manipulate the command execution flow and gain access to the underlying Linux shell environment, which operates with root privileges. The vulnerability essentially creates a command injection vector within the legitimate CLI interface, enabling attackers to execute arbitrary system commands with the highest possible privileges on the affected device. This type of vulnerability is categorized under CWE-77 and CWE-78 within the Common Weakness Enumeration framework, representing command injection flaws that allow arbitrary code execution.
The operational impact of CVE-2018-0183 extends far beyond simple privilege escalation, as it provides attackers with complete control over the affected network device. Once an attacker gains root access through this vulnerability, they can modify device configurations, disable security features, monitor network traffic, steal credentials, and establish persistent access points within the network infrastructure. The vulnerability effectively neutralizes the security boundaries that should protect the device from unauthorized access, as the attacker can now execute any command that the underlying Linux system allows, including system-level operations that could compromise the entire network. This access level allows for comprehensive network reconnaissance, data exfiltration, and potential lateral movement to other devices within the network, making it a significant threat to enterprise security. The vulnerability affects the fundamental integrity of network device security and can be exploited to create persistent backdoors that remain undetected for extended periods.
Mitigation strategies for CVE-2018-0183 primarily focus on immediate software updates and operational security measures. Cisco released patches and software updates to address this vulnerability, which should be deployed immediately on all affected devices. Network administrators should implement the principle of least privilege by limiting the number of users with privilege level 15 access and regularly auditing administrative accounts. Additional security measures include monitoring CLI command execution logs for suspicious patterns, implementing network segmentation to limit the impact of potential compromises, and establishing robust network access controls. The vulnerability demonstrates the importance of proper input validation and sanitization in security-critical applications, as highlighted by ATT&CK technique T1059.001 for Command and Scripting Interpreter. Organizations should also consider implementing intrusion detection systems to monitor for exploitation attempts and maintain comprehensive incident response procedures that account for this type of privilege escalation attack vector. Regular security assessments and vulnerability management processes are essential to prevent similar issues in other components of the network infrastructure.