CVE-2018-18858 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 system function to execute the "tun_path" or "tap_path" pathname within a shell command.
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Analysis
by VulDB Data Team • 12/25/2024
The vulnerability CVE-2018-18858 represents a critical local privilege escalation issue affecting LiquidVPN client versions through 1.37 on macOS systems. This vulnerability stems from improper access controls within the application's XPC service architecture, creating a pathway for attackers to execute arbitrary commands with root privileges. The flaw specifically resides in the com.smr.liquidvpn.OVPNHelper service which lacks proper authentication mechanisms, allowing unauthorized users to communicate with this unprotected service and leverage it for malicious purposes.
The technical implementation of this vulnerability involves the exploitation of a dangerous system function that executes shell commands without proper input sanitization. When the application processes the "tun_path" or "tap_path" parameters, it directly incorporates these values into shell command execution contexts without adequate validation or escaping. This creates a classic command injection vulnerability where attacker-controlled input can be interpreted and executed as shell commands by the system. The vulnerability manifests through the use of system functions that should never be exposed to untrusted input sources, particularly in privileged contexts where such exposure can lead to complete system compromise.
The operational impact of this vulnerability is severe and far-reaching, as it allows local attackers to escalate their privileges from standard user level to root access without requiring any additional exploitation techniques. Once an attacker gains access to the unprotected XPC service, they can execute arbitrary commands with the highest system privileges, effectively bypassing all standard security controls and user access restrictions. This capability extends to loading malicious kernel extensions, which can provide persistent backdoors or further compromise the system's integrity. The vulnerability essentially provides a direct path to system root access that bypasses traditional security boundaries and authentication mechanisms.
Mitigation strategies for this vulnerability should focus on implementing proper access controls and input validation mechanisms within the XPC service architecture. The com.smr.liquidvpn.OVPNHelper service must be configured with appropriate authentication requirements to prevent unauthorized access, and all user-supplied input must undergo strict validation and sanitization before being processed in shell contexts. Organizations should immediately update to patched versions of the LiquidVPN client where available, as the vulnerability affects multiple versions of the software. Additionally, system administrators should monitor for unauthorized kernel extension installations and implement security policies that restrict the loading of unsigned kernel modules. This vulnerability aligns with CWE-78, which describes improper neutralization of special elements in OS commands, and represents a significant risk under ATT&CK framework's privilege escalation techniques where adversaries seek to gain higher-level permissions through application flaws. The vulnerability demonstrates the critical importance of secure coding practices, particularly in privileged services where improper input handling can lead to complete system compromise.