CVE-2018-4004 in VPN
Summary
by MITRE
An exploitable privilege escalation vulnerability exists in the Shimo VPN 4.1.5.1 helper service in the disconnectService functionality. A non-root user is able to kill any privileged process on the system. An attacker would need local access to the machine for a successful exploit.
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Analysis
by VulDB Data Team • 08/29/2023
The CVE-2018-4004 vulnerability represents a critical privilege escalation flaw in the Shimo VPN 4.1.5.1 helper service that fundamentally undermines system security through improper privilege management. This vulnerability resides within the disconnectService functionality of the VPN helper service, which operates with elevated privileges to manage network connections. The flaw allows any local user, regardless of their privilege level, to execute commands that can terminate any privileged process running on the system. This represents a severe breakdown in the principle of least privilege and demonstrates poor access control implementation within the VPN application's architecture. The vulnerability is particularly concerning because it operates at the system level where it can compromise the integrity and availability of critical processes.
The technical implementation of this vulnerability stems from insufficient input validation and improper privilege separation within the helper service. When the disconnectService function is invoked, it fails to properly authenticate or authorize the requesting user before executing process termination commands. This allows a non-root user to leverage the helper service's elevated permissions to kill processes that should only be controllable by the system administrator or root user. The vulnerability is classified as a privilege escalation issue that aligns with CWE-276, which addresses improper privileges for system resources, and specifically relates to CWE-782, which covers exposed service functions with elevated privileges. The flaw operates through the helper service's IPC mechanisms that lack proper authentication checks, enabling arbitrary process termination through user-controlled inputs.
The operational impact of CVE-2018-4004 extends beyond simple privilege escalation to potentially enable complete system compromise when combined with other attack vectors. An attacker with local access can leverage this vulnerability to kill critical system processes including security services, network monitoring tools, or authentication daemons, thereby creating a denial of service condition that could persist until system reboot. This capability allows for persistent system disruption and can be used to disable security controls that would otherwise protect the system from further exploitation. The vulnerability directly maps to ATT&CK technique T1068, which covers exploit for privilege escalation, and T1489, which addresses system shutdown/reboot through service manipulation. The local access requirement does not significantly limit the attack surface since compromised local accounts often provide access to other system resources that can be leveraged for further compromise.
Mitigation strategies for CVE-2018-4004 must address both immediate remediation and long-term architectural improvements to prevent similar vulnerabilities. The most effective immediate solution involves updating to a patched version of Shimo VPN that properly validates user privileges before executing privileged operations. System administrators should also implement proper access controls to restrict the execution and modification of helper services, ensuring that only authorized users can interact with privileged components. Network segmentation and privilege separation should be enforced to prevent local users from accessing critical system services. The vulnerability highlights the importance of implementing proper privilege separation and authentication checks in system helper services, which aligns with security best practices outlined in NIST SP 800-53 and ISO 27001 controls. Organizations should also consider implementing process monitoring and alerting to detect unauthorized process termination activities that could indicate exploitation attempts. Regular security assessments of third-party applications and their helper services should be conducted to identify similar privilege escalation vulnerabilities that could be exploited to gain unauthorized system access.