CVE-2025-21197 in Windows
Summary
by MITRE • 04/08/2025
Improper access control in Windows NTFS allows an authorized attacker to disclose file path information under a folder where the attacker doesn't have permission to list content.
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Analysis
by VulDB Data Team • 05/21/2026
This vulnerability represents a critical access control flaw in the Windows NTFS file system implementation that enables authorized attackers to extract file path information from directories they lack explicit permission to enumerate. The issue stems from improper validation of access control lists and permission checks within the NTFS subsystem, where the system inadvertently reveals directory structure information even when the attacker possesses only basic read permissions. This weakness operates at the kernel level of the operating system and affects the core file system security model that governs how access permissions are enforced across different file system objects. The vulnerability can be categorized under CWE-284 which specifically addresses improper access control mechanisms, and aligns with ATT&CK technique T1005 where adversaries collect data from local systems. When an attacker successfully exploits this flaw, they can discover the existence of files and subdirectories within restricted folders without having the necessary permissions to actually access or read the contents, effectively providing them with reconnaissance information that could be leveraged for further attacks.
The technical implementation of this vulnerability occurs when the NTFS file system performs access validation checks during file path resolution operations. Under normal circumstances, when a user attempts to access a directory they don't have permission to list, the system should return a generic access denied error without revealing any information about the directory structure. However, in vulnerable implementations, the system provides information about the existence of files and folders within the restricted directory, essentially leaking path information through error handling mechanisms or access control validation routines. This typically manifests when attackers attempt to enumerate directory contents through legitimate system calls or when they use tools that interact with the file system at a lower level. The vulnerability is particularly concerning because it operates silently in the background and can be exploited by attackers who have minimal privileges within the system, making it difficult to detect through standard monitoring mechanisms.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with valuable reconnaissance data that can significantly aid in planning more sophisticated attacks against the system. When an attacker can discover file paths within restricted directories, they gain intelligence about system structure and potentially identify sensitive files or directories that may contain valuable data. This information can be used to target specific files for further exploitation or to identify potential privilege escalation opportunities within the system. The vulnerability affects system administrators who may not realize that unauthorized path information disclosure is occurring, potentially leading to extended periods of exposure without detection. Additionally, the impact is compounded when multiple vulnerable systems exist within the same network, as attackers can map out entire directory structures across different hosts, creating comprehensive attack vectors. This type of information leakage can be particularly damaging in environments where sensitive data is stored in structured directories with predictable naming conventions.
Mitigation strategies for this vulnerability should focus on implementing proper access control validation and ensuring that all system calls properly validate permissions before returning any information about file system structure. System administrators should apply the latest security patches from Microsoft that address this specific access control flaw in NTFS implementations. Additional protective measures include implementing strict file system auditing to monitor for unusual access patterns that might indicate exploitation attempts, and configuring access control lists to properly restrict directory enumeration permissions. Network segmentation and privilege separation can help limit the potential impact if an attacker successfully exploits this vulnerability, as they would only be able to discover information from directories they might otherwise have access to through legitimate means. Security monitoring solutions should be configured to detect and alert on anomalous file system access patterns that might indicate attempts to exploit this vulnerability, particularly when multiple access attempts occur against directories where the user has no apparent legitimate reason to request path information. Regular security assessments should include testing for this specific vulnerability to ensure that access control mechanisms are properly functioning and that no unauthorized path disclosure is occurring within the system.