CVE-2025-21197 is a vulnerability classified under CWE-284 (Improper Access Control) affecting Microsoft Windows 10 Version 1809 (build 10.0.17763.0). The flaw resides in the Windows NTFS file system's access control mechanisms, where an authorized attacker with limited privileges can disclose file path information within a directory for which they lack permission to list contents. Essentially, this vulnerability allows an attacker to bypass intended access restrictions and gain visibility into folder structures and file paths that should be inaccessible. The vulnerability does not allow modification or deletion of files, nor does it require user interaction to exploit. The CVSS 3.1 base score is 6.5 (medium severity), with the vector indicating network attack vector (AV:N), low attack complexity (AC:L), privileges required (PR:L), no user interaction (UI:N), unchanged scope (S:U), high confidentiality impact (C:H), no integrity or availability impact (I:N/A:N), and official remediation level (RL:O) with confirmed fix (RC:C). No known exploits are currently reported in the wild, and there are no patch links provided yet. This vulnerability could be leveraged by attackers to gather sensitive information about the file system structure, which may facilitate further targeted attacks or privilege escalation attempts.

For European organizations, the primary impact of CVE-2025-21197 lies in the potential exposure of sensitive directory and file path information that should be restricted. Disclosure of such information can aid attackers in reconnaissance activities, enabling them to map out critical data storage locations, identify valuable assets, or discover configuration files that could be leveraged in subsequent attacks. While this vulnerability does not directly compromise data integrity or availability, the confidentiality breach can have significant consequences, especially for organizations handling sensitive personal data, intellectual property, or critical infrastructure information. This is particularly relevant under the GDPR framework, where unauthorized disclosure of personal data or system details may lead to compliance violations and regulatory penalties. Additionally, attackers could use the disclosed information to craft more effective phishing or social engineering campaigns targeting European entities. Since the vulnerability requires only low privileges and no user interaction, insider threats or compromised low-level accounts could exploit this flaw to escalate their knowledge of the environment.

Given the absence of an official patch link, European organizations should implement compensating controls to mitigate the risk. These include: 1) Restricting access to Windows 10 Version 1809 systems and limiting user privileges to the minimum necessary, especially for accounts that do not require directory listing capabilities. 2) Employing strict network segmentation and access controls to reduce exposure of vulnerable systems. 3) Monitoring file system access logs and unusual directory enumeration attempts to detect potential exploitation attempts. 4) Utilizing endpoint detection and response (EDR) tools to identify suspicious activities related to file system access. 5) Planning and prioritizing an upgrade to a more recent and supported Windows version where this vulnerability is fixed or mitigated. 6) Applying principle of least privilege rigorously and reviewing group policies related to NTFS permissions to ensure no excessive rights are granted. 7) Educating IT staff about the vulnerability and encouraging vigilance for related indicators of compromise. Once Microsoft releases an official patch, immediate deployment should be prioritized.