CVE-2018-4008 in VPN
Summary
by MITRE
An exploitable privilege escalation vulnerability exists in the Shimo VPN 4.1.5.1 helper service in the RunVpncScript command. The command takes a user-supplied script argument and executes it under root context. A user with local access can use this vulnerability to raise their privileges to root. An attacker would need local access to the machine to successfully exploit this bug.
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Analysis
by VulDB Data Team • 08/29/2023
The vulnerability described in CVE-2018-4008 represents a critical privilege escalation flaw within the Shimo VPN 4.1.5.1 helper service that operates with elevated privileges. This issue stems from the RunVpncScript command implementation which improperly handles user-supplied script arguments, creating a dangerous execution path that allows arbitrary code execution under root context. The vulnerability specifically affects the helper service component that is designed to manage VPN connections and execute necessary scripts during the connection process, but fails to properly validate or sanitize input parameters before executing them with elevated privileges.
The technical flaw manifests in the improper execution model where the helper service accepts a script argument from user input and directly executes it without adequate security controls or privilege separation. This design flaw falls under CWE-78 which specifically addresses improper neutralization of special elements used in OS commands, and CWE-20 which covers improper input validation. The vulnerability exists because the system fails to implement proper input sanitization and privilege separation mechanisms, allowing a malicious user to inject arbitrary commands that will be executed with root privileges. The attack vector requires local access to the target machine, making it a local privilege escalation vulnerability that can be exploited by any user with access to the system.
The operational impact of this vulnerability is severe as it allows any local user to escalate their privileges to root level access, effectively compromising the entire system. This privilege escalation capability enables attackers to bypass standard access controls, modify system files, install malicious software, and potentially access sensitive data. The vulnerability essentially provides a backdoor mechanism for privilege elevation that could be exploited to maintain persistent access, escalate further attacks, or gain complete control over the affected system. The implications extend beyond immediate privilege escalation as it can serve as a foundation for more sophisticated attacks within the network environment.
Mitigation strategies should focus on immediate patching of the Shimo VPN application to the latest version that addresses this vulnerability. System administrators should implement privilege separation controls to ensure that helper services do not execute user-supplied scripts with elevated privileges. The principle of least privilege should be enforced by modifying the helper service to validate and sanitize all input parameters before execution, and to run with minimal required privileges rather than root access. Additional defensive measures include implementing file integrity monitoring to detect unauthorized modifications to the VPN helper service, restricting local access to the system, and conducting regular security assessments to identify similar privilege escalation vulnerabilities in other system components. Organizations should also consider implementing application whitelisting policies to prevent unauthorized execution of potentially malicious scripts. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques, specifically T1068 which addresses local privilege escalation, and T1548 which covers abuse of group privileges, making it a significant concern for enterprise security posture and incident response planning.