CVE-2025-27738 in Windows
Summary
by MITRE • 04/08/2025
Improper access control in Windows Resilient File System (ReFS) allows an authorized attacker to disclose information over a network.
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Analysis
by VulDB Data Team • 04/08/2025
The vulnerability under discussion involves improper access control within the Windows Resilient File System ReFS implementation, representing a significant security weakness that could be exploited by authorized attackers to gain unauthorized information disclosure over network connections. This issue stems from insufficient validation mechanisms within the file system's network communication protocols, particularly when handling remote access requests to ReFS volumes.
The technical flaw manifests in how ReFS processes network-based file operations and access requests, where the system fails to properly enforce access control policies during remote file transfers or directory listings. Specifically, the vulnerability occurs when authorized users attempt to access ReFS volumes through network shares or remote protocols, allowing them to potentially bypass normal permission checks and retrieve sensitive data that should be restricted. This improper access control mechanism operates at the protocol level within the Windows file system stack, particularly affecting how ReFS handles authentication tokens and access validation during network operations.
The operational impact of this vulnerability extends beyond simple information disclosure, as it could enable attackers with legitimate network access to escalate their privileges or conduct reconnaissance activities on otherwise protected storage volumes. The attack surface includes any environment where ReFS volumes are exposed through network protocols such as SMB/CIFS, making it particularly dangerous in enterprise environments where multiple users share network resources. Organizations may experience unauthorized data exposure, potential compliance violations, and increased risk of lateral movement attacks that could compromise additional system components.
Mitigation strategies should focus on implementing proper network segmentation to limit access to ReFS volumes, enforcing strict access control policies through Windows Group Policy configurations, and applying timely security updates from Microsoft that address the specific access control weaknesses. Network administrators should also consider disabling unnecessary file sharing protocols, implementing network monitoring solutions to detect anomalous access patterns, and conducting regular security assessments to identify potential exploitation attempts. The vulnerability aligns with CWE-284 Access Control Issues and could be categorized under ATT&CK technique T1074 Data Staged for exfiltration, emphasizing the importance of proper access control enforcement in file system implementations.
This weakness highlights the critical need for robust access control mechanisms within storage systems, particularly those designed for high availability and fault tolerance like ReFS. The vulnerability demonstrates how even authorized users can exploit implementation gaps in network protocols to gain unauthorized information access, underscoring the importance of defense-in-depth strategies that include both perimeter security measures and internal access controls. Organizations should also consider implementing automated patch management processes to ensure timely deployment of Microsoft security updates that address such access control vulnerabilities, particularly in environments where ReFS volumes are actively used for network storage solutions.