CVE-2018-7281 in CactusVPN
Summary
by MITRE
CactusVPN 5.3.6 for macOS contains a root privilege escalation vulnerability through a setuid root binary called runme. The binary takes a single command line argument and passes this argument to a system() call, thus allowing low privileged users to execute commands as root.
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Analysis
by VulDB Data Team • 01/07/2020
The vulnerability identified as CVE-2018-7281 represents a critical privilege escalation flaw within CactusVPN version 5.3.6 for macOS systems. This security weakness stems from the presence of a setuid root binary named runme which is designed to execute with elevated privileges. The flaw manifests when the application processes command line arguments without proper validation or sanitization, creating an exploitable path for malicious actors to gain root access. The vulnerability specifically targets the macOS platform and affects users who have installed the affected version of the VPN client software.
The technical implementation of this vulnerability follows a classic command injection pattern where the setuid binary accepts user input and directly passes it to the system() function call. This design flaw allows unprivileged users to craft malicious command line arguments that get executed with root privileges. The system() function in C is particularly dangerous in this context because it invokes the shell to execute commands, making it susceptible to various shell injection techniques. The vulnerability is classified under CWE-78 as "Improper Neutralization of Special Elements used in a Command ('Command Injection')", which is a well-documented weakness in software security practices. Attackers can exploit this by providing specially crafted arguments that leverage shell metacharacters to execute arbitrary commands, potentially leading to complete system compromise.
The operational impact of this vulnerability is severe as it fundamentally undermines the security model of the macOS system. Any user with access to the CactusVPN application can escalate their privileges to root level, enabling them to modify system files, install malware, access sensitive data, or completely compromise the affected system. This privilege escalation occurs without requiring authentication or additional exploitation steps beyond the initial installation of the vulnerable software. The attack surface is particularly concerning because VPN applications often run with elevated privileges to manage network connections, making them attractive targets for attackers seeking persistent access. From an ATT&CK framework perspective, this vulnerability maps to T1068 (Exploitation for Privilege Escalation) and T1548.001 (Abuse Elevation Control Mechanism), representing a clear path for adversaries to establish persistent control over affected systems.
Mitigation strategies for this vulnerability should focus on immediate remediation through software updates from the vendor, which would address the improper input handling and remove the vulnerable setuid binary. System administrators should implement monitoring for unusual execution patterns of the runme binary and establish proper access controls to limit user interaction with potentially dangerous applications. The principle of least privilege should be enforced by ensuring that applications do not run with unnecessary elevated privileges. Additionally, network segmentation and application whitelisting can help prevent exploitation even if the vulnerability exists in the environment. Regular security audits should verify that setuid binaries are properly configured and that no unnecessary elevated privileges exist in the system. Organizations should also consider implementing automated patch management systems to ensure timely updates and reduce exposure windows for known vulnerabilities.