CVE-2025-27483 Overview
CVE-2025-27483 is an out-of-bounds read vulnerability [CWE-125] in the Windows NTFS file system driver. An attacker with local access can read memory outside the bounds of an allocated buffer to elevate privileges on affected Windows systems. Exploitation requires user interaction, such as opening a malicious file or mounting a crafted volume. Successful exploitation grants the attacker elevated privileges with high impact on confidentiality, integrity, and availability. Microsoft published the advisory on April 8, 2025, and the issue affects multiple supported Windows client and server editions, including Windows 10 versions 1507, 1607, and 1809, as well as Windows Server 2012 R2, 2016, and 2019.
Critical Impact
Local attackers can leverage a crafted NTFS structure to read out-of-bounds memory and escalate privileges, potentially gaining SYSTEM-level access on unpatched Windows hosts.
Affected Products
- Microsoft Windows 10 versions 1507, 1607, and 1809 (x86 and x64)
- Microsoft Windows Server 2012 R2 and Windows Server 2016
- Microsoft Windows Server 2019
Discovery Timeline
- 2025-04-08 - CVE-2025-27483 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-27483
Vulnerability Analysis
The flaw resides in the NTFS driver responsible for parsing on-disk file system structures. NTFS handles file metadata such as Master File Table (MFT) entries, attribute headers, and index records. When the driver processes a malformed structure, it reads data past the end of an allocated buffer. This out-of-bounds read exposes adjacent kernel memory contents to the calling context.
Attackers chain the information disclosure with other primitives to bypass kernel address space layout randomization (KASLR) or to leak privileged data. Combined with a separate write primitive, the leak supports a reliable local privilege escalation chain. The CWE-125 classification confirms the root issue is a read past a buffer boundary rather than a write corruption.
Root Cause
The vulnerability stems from insufficient validation of length or offset fields within NTFS metadata structures. The driver trusts attacker-controlled size values when copying or parsing records. When the supplied length exceeds the allocated buffer, the parser dereferences memory beyond the intended region.
Attack Vector
Exploitation requires local access and user interaction. A common scenario involves a user mounting a malicious virtual hard disk (VHD) or external storage device containing a crafted NTFS volume. When the file system driver parses the volume, the out-of-bounds read triggers. Network or remote exploitation is not viable based on the published attack vector.
No public proof-of-concept code, exploit module, or CISA Known Exploited Vulnerabilities listing exists for this CVE at the time of writing. Refer to the Microsoft Security Update Guide for CVE-2025-27483 for vendor-supplied technical details.
Detection Methods for CVE-2025-27483
Indicators of Compromise
- Unexpected mounting of VHD, VHDX, or ISO files from user-writable directories or removable media.
- Kernel-mode crashes or bug checks referencing ntfs.sys shortly after a user opens external storage.
- Creation of new privileged accounts or services following a file-open event involving an untrusted volume.
Detection Strategies
- Monitor Windows event logs for disk mount operations (Event IDs 98, 507) tied to untrusted file sources.
- Hunt for processes spawning cmd.exe or powershell.exe with SYSTEM integrity immediately after non-administrative users interact with removable media.
- Apply behavioral identification rules that flag privilege transitions from medium to high integrity without a corresponding User Account Control (UAC) prompt.
Monitoring Recommendations
- Forward NTFS driver crash dumps and Windows Error Reporting telemetry to a central analytics platform for correlation.
- Track file-system filter driver alerts on hosts running the affected Windows 10 1507, 1607, 1809, and Windows Server 2012 R2, 2016, and 2019 builds.
- Alert on attempts to attach VHD or VHDX files via diskpart, Mount-DiskImage, or Explorer shell extensions in user sessions.
How to Mitigate CVE-2025-27483
Immediate Actions Required
- Apply the Microsoft security updates referenced in the Microsoft Security Update Guide for CVE-2025-27483 to all affected Windows builds.
- Inventory endpoints and servers running Windows 10 1507, 1607, 1809, and Windows Server 2012 R2, 2016, and 2019, and prioritize patch deployment.
- Restrict mounting of disk images and removable media for standard user accounts through Group Policy.
Patch Information
Microsoft addressed CVE-2025-27483 in cumulative updates released through the April 2025 Patch Tuesday cycle. Administrators should consult the Microsoft Security Update Guide for CVE-2025-27483 for the specific KB articles aligned to each affected build. Verify deployment using Windows Update for Business, WSUS, or Microsoft Configuration Manager reports.
Workarounds
- Disable auto-mount of removable media and block VHD/VHDX attachment for non-administrative users via Group Policy or AppLocker.
- Apply the principle of least privilege so users cannot introduce arbitrary file systems to managed endpoints.
- Enforce attack surface reduction rules that block untrusted USB and disk image execution where business processes allow.
# Disable mounting of VHD/VHDX files for standard users via Group Policy registry key
reg add "HKLM\SOFTWARE\Policies\Microsoft\Windows\RemovableStorageDevices" /v Deny_All /t REG_DWORD /d 1 /f
# Verify installed updates after patch deployment
wmic qfe list brief /format:table
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
