CVE-2018-9105 in NordVPN
Summary
by MITRE
NordVPN 3.3.10 for macOS suffers from a root privilege escalation vulnerability. The vulnerability stems from its privileged helper tool's implemented XPC service. This XPC service is responsible for receiving and processing new OpenVPN connection requests from the main application. Unfortunately this XPC service is not protected, which allows arbitrary applications to connect and send it XPC messages. An attacker can send a crafted XPC message to the privileged helper tool requesting it make a new OpenVPN connection. Because he or she controls the contents of the XPC message, the attacker can specify the location of the openvpn executable, which could point to something malicious they control located on disk. Without validation of the openvpn executable, this will give the attacker code execution in the context of the privileged helper tool.
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Analysis
by VulDB Data Team • 02/06/2021
The vulnerability identified as CVE-2018-9105 represents a critical privilege escalation flaw in NordVPN version 3.3.10 for macOS systems. This security weakness specifically targets the application's privileged helper tool that operates through an XPC (Cross-Process Communication) service interface. The XPC service serves as a communication bridge between the main NordVPN application and its privileged helper component, facilitating the processing of OpenVPN connection requests. The fundamental flaw lies in the absence of proper access controls and message validation within this XPC service implementation, creating an exploitable attack vector that bypasses normal security boundaries.
The technical exploitation of this vulnerability occurs through the manipulation of XPC communication protocols, where unauthenticated applications can establish connections to the privileged helper tool. When an attacker crafts and sends a malicious XPC message through this unprotected interface, they can influence the execution context of the helper tool by specifying arbitrary paths to the openvpn executable. This design flaw allows attackers to redirect the execution flow to malicious binaries controlled by the attacker, effectively executing code with elevated privileges that should normally be restricted to the privileged helper process. The vulnerability directly maps to CWE-284 (Improper Access Control) and CWE-78 (Improper Neutralization of Special Elements used in OS Command Injection), as the system fails to validate input parameters and properly restrict access to privileged operations.
The operational impact of this privilege escalation vulnerability is severe and far-reaching for affected macOS systems. An attacker who successfully exploits this flaw can execute arbitrary code with root privileges, effectively gaining complete control over the compromised system. This elevated access enables malicious actors to install persistent backdoors, modify system files, access encrypted data, and potentially establish further footholds within network environments. The vulnerability affects the core security model of the NordVPN application, as it undermines the principle of least privilege by allowing untrusted processes to manipulate privileged components. The attack vector is particularly concerning because it requires minimal user interaction and can be exploited through standard application communication channels.
Mitigation strategies for this vulnerability should focus on implementing proper access controls and input validation within the XPC service architecture. System administrators should immediately update to NordVPN versions that address this privilege escalation flaw, as the vendor has released patches to fix the unprotected XPC service. Additionally, organizations should implement monitoring solutions that detect unauthorized XPC communication attempts and review system configurations to ensure that only trusted applications can communicate with privileged helper tools. The remediation process should include verifying that the XPC service properly validates all incoming messages and implements strict authentication mechanisms to prevent unauthorized access to privileged operations. This vulnerability demonstrates the critical importance of secure communication protocols in privileged helper tools and aligns with ATT&CK technique T1068 (Local Port Forwarding) and T1548.1 (Abuse Elevation Control Mechanism) in threat modeling frameworks.