CVE-2018-18859 in LiquidVPN Client
Summary
by MITRE
Multiple local privilege escalation vulnerabilities have been identified in the LiquidVPN client through 1.37 for macOS. An attacker can communicate with an unprotected XPC service and directly execute arbitrary OS commands as root or load a potentially malicious kernel extension because com.smr.liquidvpn.OVPNHelper uses the value of the "tun_path" or "tap_path" pathname in a kextload() call.
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Analysis
by VulDB Data Team • 12/25/2024
The vulnerability CVE-2018-18859 represents a critical local privilege escalation issue within the LiquidVPN client version 1.37 for macOS operating systems. This flaw stems from improper security controls within the application's communication mechanisms, specifically targeting an unprotected XPC service that facilitates communication between user-space processes and privileged system components. The vulnerability exists in the com.smr.liquidvpn.OVPNHelper service which fails to properly validate input parameters before executing system-level operations. Attackers can exploit this weakness by directly communicating with the vulnerable XPC service and manipulating the tun_path or tap_path parameters, which are then used in subsequent kextload() system calls without adequate sanitization or access control validation.
The technical implementation of this vulnerability demonstrates a classic improper input validation flaw that maps to CWE-20, which describes improper input validation in software systems. The core issue manifests when the OVPNHelper service processes user-provided pathname values from the tun_path or tap_path parameters, directly incorporating these values into kernel extension loading operations. This creates an environment where arbitrary code execution becomes possible through privilege escalation, as the system executes kernel-level operations with elevated privileges. The vulnerability specifically leverages the lack of proper parameter validation in the kextload() function call, allowing attackers to inject malicious kernel extension paths that will be loaded with root privileges. This represents a significant bypass of macOS security mechanisms including System Integrity Protection and kernel extension validation policies.
The operational impact of CVE-2018-18859 is severe and multifaceted within macOS environments. Successful exploitation allows attackers to achieve complete system compromise through privilege escalation to root level access, enabling them to install persistent backdoors, modify system files, disable security controls, and exfiltrate sensitive data without detection. The vulnerability affects any macOS system running LiquidVPN client version 1.37 or earlier, making it particularly dangerous in enterprise environments where VPN clients are commonly deployed. The attack vector is particularly concerning because it requires no network connectivity or user interaction beyond having the vulnerable VPN client installed, making it a latent threat that can be exploited by attackers who gain local access to a compromised system. This vulnerability directly maps to attack techniques described in the MITRE ATT&CK framework under privilege escalation tactics, specifically targeting the execution of malicious code with elevated privileges.
Mitigation strategies for CVE-2018-18859 must focus on immediate remediation through software updates and system hardening measures. The primary solution involves upgrading to a patched version of the LiquidVPN client that properly validates input parameters before executing privileged operations. System administrators should also implement additional security controls including disabling unnecessary XPC services, monitoring for unauthorized kernel extension loading activities, and enforcing strict access controls on privileged system components. The vulnerability highlights the importance of proper input validation and privilege separation in macOS security architecture, with recommendations aligning with the principle of least privilege and secure coding practices. Organizations should conduct comprehensive vulnerability assessments to identify other potentially vulnerable applications and services, while implementing continuous monitoring for suspicious kernel extension loading patterns that could indicate exploitation attempts. The remediation process should include verification that the patched version properly enforces parameter validation and that no lingering vulnerabilities remain in the system's privilege escalation pathways.