CVE-2018-0184 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: CSCve74432.
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Analysis
by VulDB Data Team • 02/06/2021
The vulnerability described in CVE-2018-0184 represents a critical privilege escalation flaw within Cisco IOS XE Software that demonstrates a fundamental failure in input validation and command parsing mechanisms. This vulnerability exists within the Command Line Interface parser of the software, which serves as the primary interface for network administrators to interact with Cisco devices. The flaw allows an authenticated attacker with privileged EXEC mode access to bypass normal security boundaries and access the underlying Linux shell that powers the device's operating system. This represents a severe architectural weakness where the software fails to properly sanitize command arguments, creating an attack surface that directly enables arbitrary code execution with the highest possible privileges. The vulnerability specifically affects devices running Cisco IOS XE Software where the CLI parser does not adequately validate or escape user-supplied arguments before processing them within the system's internal data structures.
The technical exploitation of this vulnerability requires an attacker to already possess privilege level 15 access, which represents the highest administrative privileges within Cisco IOS. However, this prerequisite does not diminish the severity of the flaw, as it still provides a path to complete system compromise from within the administrative environment. The vulnerability stems from improper argument sanitization where crafted command arguments can manipulate the CLI parser to access internal system functions that should remain protected. When an attacker executes a specially crafted CLI command, the parser fails to properly validate the input and allows the underlying Linux shell to be accessed directly. This creates a direct pathway for privilege escalation from the administrative context to root privileges, enabling the execution of arbitrary commands with complete system control. The flaw essentially removes the boundary protection that should exist between the CLI interface and the underlying operating system, allowing unauthorized access to system-level functionality.
The operational impact of this vulnerability extends far beyond simple command execution, as it fundamentally compromises the security model of Cisco network devices. An attacker who successfully exploits this vulnerability can gain complete control over the affected device, potentially leading to network disruption, data exfiltration, or use as a pivot point for attacking other systems within the network. The vulnerability affects the core operational integrity of network infrastructure, as it allows attackers to bypass the standard security controls that protect network devices from unauthorized access. Organizations relying on Cisco IOS XE Software for their network infrastructure face significant risk, as the vulnerability can be exploited by insiders or external attackers who have already gained administrative access to the device. This represents a critical failure in the principle of least privilege, where the system should prevent escalation from administrative to root privileges but instead facilitates it through improper input handling.
Mitigation strategies for CVE-2018-0184 focus on both immediate remediation and long-term architectural improvements to prevent similar vulnerabilities. Cisco has released software updates and patches to address this specific vulnerability, which should be implemented immediately across all affected devices. Organizations should also implement additional monitoring and logging to detect suspicious CLI command usage that might indicate exploitation attempts. The vulnerability aligns with CWE-78 and CWE-88 categories related to command injection and improper input sanitization, and it maps to ATT&CK techniques such as privilege escalation and command and control. Network administrators should review and restrict CLI access to only necessary personnel, implement strict access controls, and regularly audit administrative activities on network devices. Additionally, organizations should consider implementing network segmentation and monitoring solutions to detect unauthorized access attempts and command execution patterns that could indicate exploitation of this vulnerability. The incident highlights the importance of proper input validation and the need for robust security boundaries within operating system interfaces to prevent unauthorized access to underlying system functionality.