CVE-2025-61871 is a security vulnerability identified in BUFFALO INC.'s NAS Navigator2 Windows client software versions prior to 3.12.0. The vulnerability stems from the registration of a Windows service with an unquoted file path. In Windows, when a service path contains spaces but is not enclosed in quotes, the system may misinterpret the path and execute malicious binaries placed in certain locations along the path. This is known as an unquoted service path vulnerability or unquoted search path element vulnerability. An attacker who has write permissions to the root directory of the system drive (e.g., C:\) can place a malicious executable with a crafted name that Windows will execute with SYSTEM privileges during service startup or restart. This effectively allows privilege escalation from a user with write access to SYSTEM-level code execution. The vulnerability requires local access with write permissions on the root drive but does not require user interaction. The CVSS v3.0 score of 6.7 reflects a medium severity, with attack vector local, low attack complexity, high privileges required, no user interaction, and high impact on confidentiality, integrity, and availability. No public exploits have been reported yet, but the vulnerability is significant due to the high privilege escalation potential. The affected product is specifically the Windows version of NAS Navigator2, a utility used to manage BUFFALO NAS devices, which are commonly deployed in enterprise and SMB environments for network-attached storage management.

For European organizations, this vulnerability poses a risk of local privilege escalation on Windows systems running NAS Navigator2 prior to version 3.12.0. If an attacker gains write access to the root directory of the system drive—potentially through other vulnerabilities, misconfigurations, or insider threats—they could execute arbitrary code with SYSTEM privileges. This could lead to full system compromise, unauthorized access to sensitive data stored on NAS devices, disruption of NAS management operations, and lateral movement within the network. Organizations relying on BUFFALO NAS devices for critical data storage or backup may face confidentiality breaches, data integrity issues, and availability disruptions. The impact is particularly concerning in environments with shared or insufficiently restricted access to Windows systems managing NAS devices. Although exploitation requires local access, the elevated privileges gained could facilitate further attacks, including deployment of ransomware or advanced persistent threats targeting European enterprises.

European organizations should immediately verify the version of NAS Navigator2 deployed on Windows systems and upgrade to version 3.12.0 or later where this vulnerability is fixed. If upgrading is not immediately feasible, organizations should restrict write permissions to the root directory of system drives to trusted administrators only, preventing unprivileged users from placing malicious executables. Implement application whitelisting and endpoint protection solutions that can detect or block unauthorized service path modifications or suspicious executables in system directories. Regularly audit service configurations for unquoted paths and correct them manually if necessary. Employ the principle of least privilege to limit user permissions on systems managing NAS devices. Additionally, monitor system logs for unusual service restarts or execution of unexpected binaries. Network segmentation can limit the impact of a compromised system. Finally, educate system administrators about this vulnerability and ensure timely patch management processes are in place.