CVE-2017-20218 in Serviio Pro
Summary
by MITRE • 03/16/2026
Serviio PRO 1.8 contains an unquoted search path vulnerability in the Windows service that allows local users to execute arbitrary code with elevated privileges by placing malicious executables in the system root path. Additionally, improper directory permissions with full access for the Users group allow authenticated users to replace the executable file with arbitrary binaries, enabling privilege escalation during service startup or system reboot.
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Analysis
by VulDB Data Team • 03/16/2026
The vulnerability identified as CVE-2017-20218 affects Serviio PRO version 1.8 and represents a critical security flaw in the Windows service implementation that stems from improper handling of search paths and directory permissions. This issue creates a pathway for local attackers to escalate privileges and execute arbitrary code with elevated system rights. The vulnerability manifests through two interconnected weaknesses that compound the security risk, making it particularly dangerous in environments where the service runs with elevated privileges.
The core technical flaw involves an unquoted search path vulnerability within the Windows service component of Serviio PRO. When Windows resolves paths for service executables, it follows a specific resolution order that can be exploited when path names contain spaces but lack proper quotation. In this case, the service configuration allows for arbitrary executables to be placed in the system root path, specifically the C: directory, where the system will execute any binary with the same name as the service. This behavior directly aligns with CWE-428, which describes the weakness of unquoted search paths in Windows systems, and creates a predictable execution flow that attackers can manipulate.
The vulnerability's operational impact is significant as it enables privilege escalation from standard user accounts to system-level privileges through multiple attack vectors. The improper directory permissions that grant full access to the Users group create a persistent threat where authenticated users can replace legitimate executables with malicious binaries. This allows attackers to execute arbitrary code during service startup or system reboot, effectively creating a backdoor that persists across system restarts. The attack requires minimal privileges initially but results in complete system compromise, making it particularly dangerous for enterprise environments where service accounts often run with elevated permissions.
The exploitation of this vulnerability follows established patterns documented in the MITRE ATT&CK framework under techniques such as privilege escalation through service misconfiguration and persistence mechanisms. Attackers can leverage this weakness by placing malicious executables in the system root directory where the service will execute them without proper validation. This approach bypasses many traditional security controls as the malicious code executes within the legitimate service context, making detection more challenging. The vulnerability also demonstrates the importance of proper privilege separation and secure configuration practices as outlined in security frameworks like NIST SP 800-53.
Mitigation strategies should focus on immediate remediation through proper service configuration and directory permission adjustments. The service configuration must be updated to use properly quoted paths to prevent unquoted search path exploitation. Directory permissions should be restricted to prevent the Users group from having full access to service directories, following the principle of least privilege. Additionally, implementing application whitelisting controls and regular security audits of service configurations can help detect and prevent similar vulnerabilities. The service should be configured to run with minimal required privileges, and regular patching schedules should be implemented to address known vulnerabilities in third-party software components. Organizations should also consider implementing monitoring solutions that can detect unauthorized file modifications to service directories, providing early warning of potential exploitation attempts.