CVE-2017-16757 in VPN
Summary
by MITRE
Hola VPN 1.34 has weak permissions (Everyone:F) under %PROGRAMFILES%, which allows local users to gain privileges via a Trojan horse 7za.exe or hola.exe file.
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Analysis
by VulDB Data Team • 12/05/2019
The vulnerability identified as CVE-2017-16757 represents a critical privilege escalation flaw in Hola VPN version 1.34 that stems from improper file system permissions within the Windows operating environment. This weakness specifically manifests in the program files directory where the application's components are installed with overly permissive access controls granting full file system permissions to the Everyone group. The affected directory structure contains executable files that are vulnerable to manipulation by local attackers who can exploit these weak permissions to elevate their system privileges.
The technical exploitation mechanism relies on the Trojan horse attack pattern where malicious actors place specially crafted executable files named 7za.exe or hola.exe within the vulnerable program files directory. When the legitimate Hola VPN application attempts to execute these files, the system executes the malicious binaries with elevated privileges, effectively allowing the attacker to run arbitrary code with administrative rights. This vulnerability directly maps to CWE-276, which addresses incorrect permissions for critical system resources, and represents a classic example of insecure file permissions that enable privilege escalation attacks.
The operational impact of this vulnerability extends beyond simple local privilege escalation as it provides attackers with persistent access to the compromised system. Once elevated to administrator level, the malicious actor can install additional malware, modify system configurations, access sensitive data, and potentially establish backdoors for continued unauthorized access. The attack vector is particularly concerning because it requires minimal sophistication and can be executed by any local user, making it an attractive target for both casual attackers and more organized threat groups seeking to establish persistent presence within network environments.
Security professionals should note that this vulnerability demonstrates the importance of proper access control implementation and the principle of least privilege in application deployment. The weakness indicates a failure in the application's security hardening process and highlights the need for comprehensive permission auditing of installed software components. Organizations should implement immediate mitigations including restricting permissions on the Hola VPN program files directory, removing the vulnerable application, and conducting thorough audits of installed software for similar permission issues. This vulnerability aligns with ATT&CK technique T1068 which covers local privilege escalation through the exploitation of system vulnerabilities, and T1547 which addresses persistence mechanisms through modification of system components.
The remediation approach should involve immediate removal of the vulnerable Hola VPN application from all affected systems followed by proper permission reconfiguration of the program files directory. System administrators should also implement regular security assessments to identify applications with overly permissive file system configurations and ensure that all software installations follow security best practices. Additionally, endpoint protection solutions should be configured to monitor for unauthorized executable modifications in program files directories, providing visibility into potential exploitation attempts of similar vulnerabilities.