CVE-2018-4007 in VPN
Summary
by MITRE
An exploitable privilege escalation vulnerability exists in the Shimo VPN 4.1.5.1 helper service in the deleteConfig functionality. The program is able to delete any protected file on the system. An attacker would need local access to the machine to successfully exploit the bug.
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Analysis
by VulDB Data Team • 08/29/2023
The CVE-2018-4007 vulnerability represents a critical privilege escalation flaw within the Shimo VPN 4.1.5.1 helper service, specifically within its deleteConfig functionality. This vulnerability stems from inadequate input validation and insufficient access controls within the privileged helper service component. The flaw allows an attacker with local system access to execute arbitrary file deletion commands against protected system files, effectively bypassing normal file system permissions and access controls. The vulnerability is particularly concerning because it operates within a privileged context, meaning that any file deletion command executed through this functionality can target system-critical files without proper authorization checks. The helper service architecture typically runs with elevated privileges to perform administrative tasks, but this particular implementation fails to properly validate the file paths or enforce proper access controls during the deletion process. This creates a scenario where malicious input can be used to target sensitive system files, configuration files, or even security-related binaries that should remain protected from unauthorized modification or deletion.
The technical implementation of this vulnerability demonstrates a classic case of improper input validation and privilege separation issues. When the deleteConfig functionality is invoked, the helper service does not properly sanitize or validate the file paths passed to it, allowing attackers to supply malicious file paths that could target protected system resources. The vulnerability operates under CWE-22 which specifically addresses improper limitation of a pathname to a restricted directory, commonly known as path traversal attacks. This weakness enables attackers to manipulate the file system by specifying paths that would normally be restricted, allowing access to files outside of intended directories. The privilege escalation aspect of this vulnerability is particularly dangerous because it leverages the helper service's elevated privileges to perform destructive operations that would normally be impossible for regular user processes. The attack requires only local access to the system, making it relatively easy to exploit in scenarios where an attacker has already gained user-level access, such as through phishing attacks, social engineering, or other initial compromise methods. This local privilege escalation vulnerability can be particularly devastating in enterprise environments where VPN clients are widely deployed and may have elevated privileges for legitimate administrative purposes.
The operational impact of CVE-2018-4007 extends beyond simple file deletion capabilities and represents a significant threat to system integrity and availability. An attacker who successfully exploits this vulnerability can potentially disrupt critical system operations by deleting essential configuration files, security binaries, or system libraries that are required for normal system operation. The ability to delete protected files opens the door to various attack vectors including system instability, complete system compromise, or the installation of persistent backdoors by replacing critical system files with malicious equivalents. The vulnerability's exploitation aligns with ATT&CK technique T1068 which covers 'Local Privilege Escalation' and T1059 which covers 'Command and Scripting Interpreter', as attackers can leverage the helper service to execute arbitrary commands with elevated privileges. In practical terms, this vulnerability could allow an attacker to delete system logs, security certificates, network configuration files, or even critical VPN client components, leading to service disruption, data loss, or complete system compromise. The impact is particularly severe in environments where the Shimo VPN client is used for enterprise network access, as the attacker could potentially disable network connectivity or access controls, creating a persistent threat vector. Additionally, the vulnerability demonstrates poor security practices in the design of privileged helper services, where proper input validation and privilege separation have been neglected, creating a dangerous attack surface that could be leveraged for more sophisticated attacks.
Mitigation strategies for CVE-2018-4007 should focus on both immediate remediation and long-term architectural improvements. The most effective immediate solution involves updating to a patched version of the Shimo VPN client where the helper service properly validates all file paths and enforces appropriate access controls. Organizations should also implement strict access controls and monitoring for the helper service components, ensuring that only authorized processes can invoke the deleteConfig functionality. The vulnerability highlights the importance of proper privilege separation and input validation in privileged helper services, making it essential to review all similar components within the system for comparable weaknesses. Security monitoring should include detection of unauthorized file deletion activities, particularly targeting system-critical files, and implementation of file integrity monitoring solutions to detect unauthorized modifications. System administrators should also consider implementing application whitelisting policies to restrict which processes can communicate with the vulnerable helper service, and regular security audits should be conducted to identify and remediate similar privilege escalation vulnerabilities. The vulnerability serves as a reminder of the critical importance of secure coding practices in privileged components, particularly the need to validate all inputs and enforce proper access controls to prevent unauthorized access to system resources. Organizations should also consider implementing principle of least privilege concepts for all helper services and ensure that any elevated privilege operations are properly audited and monitored to prevent exploitation of similar vulnerabilities in the future.