CVE-2025-66271 is a security vulnerability identified in the Clone for Windows software developed by ELECOM CO.,LTD., affecting versions prior to 2.36. The issue arises from the registration of a Windows service with an unquoted file path. In Windows, unquoted service paths containing spaces can be exploited by placing malicious executables in specific locations along the search path, leading the system to execute these malicious files with the service's privileges. In this case, a user who has write permissions on the root directory of the system drive (typically C:\) can place a crafted executable that will be run with SYSTEM-level privileges when the service starts or restarts. This vulnerability is significant because SYSTEM privileges represent the highest level of access on a Windows system, allowing full control over the affected machine. The vulnerability requires that the attacker already has some level of write access to the system drive root, which is typically restricted but may be granted in misconfigured environments or through other privilege escalation techniques. The CVSS 3.0 base score of 6.7 reflects a medium severity, with attack vector local (AV:L), low attack complexity (AC:L), high privileges required (PR:H), no user interaction (UI:N), unchanged scope (S:U), and high impact on confidentiality, integrity, and availability (C:H/I:H/A:H). No known exploits have been reported in the wild as of the publication date, but the vulnerability presents a clear risk if leveraged by an attacker. The lack of a patch link suggests that users should monitor ELECOM's official channels for updates or consider workarounds to mitigate risk until a patch is available.

For European organizations, this vulnerability poses a risk of local privilege escalation leading to full system compromise. Attackers who gain write access to the system drive root—potentially through other vulnerabilities, insider threats, or misconfigurations—could exploit this flaw to execute arbitrary code with SYSTEM privileges. This could result in unauthorized access to sensitive data, disruption of critical services, and potential lateral movement within networks. Organizations in sectors with high security requirements, such as finance, healthcare, and critical infrastructure, could face significant operational and reputational damage. The vulnerability’s impact is heightened in environments where ELECOM's Clone for Windows software is deployed on critical systems. Since the attack requires local access with elevated privileges, the threat is more relevant in scenarios involving insider threats or chained attacks where initial access has been obtained. The absence of known exploits in the wild currently reduces immediate risk but does not eliminate the potential for future exploitation.

European organizations should implement the following specific mitigation measures: 1) Immediately audit and restrict write permissions on the root directory of the system drive to trusted administrators only, preventing unauthorized users from placing malicious executables. 2) Monitor and review Windows service configurations for unquoted service paths, especially for Clone for Windows and other third-party software, correcting any unquoted paths by quoting them properly or applying vendor patches. 3) Apply the official patch from ELECOM CO.,LTD. as soon as it becomes available for version 2.36 or later to remediate the vulnerability. 4) Employ endpoint detection and response (EDR) tools to detect suspicious file creation or execution activities in system directories. 5) Conduct regular privilege audits to ensure that users do not have unnecessary elevated permissions that could facilitate exploitation. 6) Implement application whitelisting to prevent unauthorized executables from running in sensitive directories. 7) Educate system administrators about the risks of unquoted service paths and the importance of secure service configuration. These targeted actions go beyond generic advice by focusing on the specific conditions that enable exploitation of this vulnerability.