CVE-2018-6623 in Hola
Summary
by MITRE
An issue was discovered in Hola 1.79.859. An unprivileged user could modify or overwrite the executable with arbitrary code, which would be executed the next time the service is started. Depending on the user that the service runs as, this could result in privilege escalation. The issue exists because of the SERVICE_ALL_ACCESS access right for the hola_svc and hola_updater services.
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Analysis
by VulDB Data Team • 01/12/2020
The vulnerability identified as CVE-2018-6623 represents a critical privilege escalation flaw within the Hola browser extension version 1.79.859. This security weakness stems from improper access control mechanisms that allow unprivileged users to manipulate critical system components. The flaw specifically affects the hola_svc and hola_updater services, which are designed to run with elevated privileges to perform their intended functions. The vulnerability manifests through the assignment of SERVICE_ALL_ACCESS rights to these services, creating an exploitable condition where malicious actors can gain unauthorized control over the service execution process. This type of vulnerability falls under the category of improper access control as defined by CWE-284, which addresses insufficient access control mechanisms that allow unauthorized users to access protected resources or modify system components. The affected services operate with elevated privileges, making them attractive targets for attackers seeking to escalate their privileges within the system.
The technical implementation of this vulnerability involves the manipulation of executable files that are scheduled to run with elevated privileges. When an unprivileged user can overwrite or modify these executables, they effectively gain the ability to inject arbitrary code that will execute with the privileges of the service account. This creates a persistent backdoor mechanism where the attacker's malicious code executes automatically whenever the service restarts, regardless of whether the user who originally installed the service is present. The operational impact is significant because the service typically runs with SYSTEM privileges, meaning successful exploitation would result in full system compromise. The vulnerability exists because the service configuration grants excessive permissions to the service account, violating the principle of least privilege that is fundamental to secure system design. This misconfiguration allows for unauthorized modification of service executables, creating a path for code injection attacks that bypass normal user access controls.
The exploitation of this vulnerability demonstrates the dangerous implications of overly permissive service configurations in Windows environments. Attackers can leverage this weakness to establish persistent access to systems by modifying service executables, effectively creating a stealthy method of privilege escalation that can persist across reboots. The issue becomes particularly concerning when considering that the hola_svc and hola_updater services are likely configured to run with high-privilege accounts, potentially including SYSTEM-level access. This vulnerability directly relates to ATT&CK technique T1068 which involves the exploitation of privilege escalation opportunities in service configurations, and T1543 which covers the creation of persistence mechanisms through service modifications. The risk assessment for this vulnerability is elevated because it provides a mechanism for attackers to maintain access even after initial compromise, as the modified executables will execute automatically during service restarts. Organizations with systems running affected versions of the Hola extension face significant exposure to this attack vector, particularly in environments where service accounts have elevated privileges.
Mitigation strategies for CVE-2018-6623 require immediate attention to service configuration and access control policies. System administrators should immediately review and restrict the permissions assigned to the hola_svc and hola_updater services, ensuring that they operate with the minimum necessary privileges. The SERVICE_ALL_ACCESS rights should be reduced to the specific permissions required for the services to function properly, eliminating unnecessary access that could be exploited. Additionally, implementing proper file system permissions on the service executable files will prevent unauthorized modification by unprivileged users. The recommended approach involves applying the principle of least privilege by restricting access to service executables and ensuring that only authorized administrators can modify these critical components. Organizations should also consider implementing file integrity monitoring solutions that can detect unauthorized changes to service executables, providing an additional layer of protection against this type of attack. Regular security audits of service configurations should be conducted to identify and remediate similar access control vulnerabilities, as this flaw represents a common pattern in software implementations where service accounts are granted excessive privileges. The remediation process should also include updating to the latest version of the Hola extension where this vulnerability has been addressed through proper access control implementation and privilege restriction.