CVE-2025-27733: Windows 10 1507 Privilege Escalation Flaw

CVE-2025-27733 Overview

CVE-2025-27733 is a high-severity out-of-bounds read vulnerability [CWE-125] affecting the Windows New Technology File System (NTFS) driver. The flaw allows a local, unauthenticated attacker to elevate privileges on a vulnerable system after a user interacts with crafted content. Microsoft published the advisory on April 8, 2025, covering multiple supported Windows client and server releases. Exploitation requires local access and user interaction, but successful attacks yield high impact to confidentiality, integrity, and availability. While no public proof-of-concept code exists at this time, the affected NTFS code path is reachable through normal file system operations, making the issue relevant for any Windows workstation or server environment.

Critical Impact
Successful exploitation enables local privilege escalation on Windows endpoints and servers, granting attackers SYSTEM-level access on compromised hosts.

Affected Products

Microsoft Windows 10 (versions 1507, 1607, 1809)
Microsoft Windows Server 2008 SP2 and 2008 R2 SP1
Microsoft Windows Server 2012, 2012 R2, 2016, and 2019

Discovery Timeline

2025-04-08 - CVE-2025-27733 published to NVD and Microsoft released the security advisory
2025-07-10 - Last updated in NVD database

Technical Details for CVE-2025-27733

Vulnerability Analysis

The vulnerability is an out-of-bounds read [CWE-125] in the Windows NTFS driver. NTFS parses on-disk metadata structures such as Master File Table (MFT) records, attribute headers, and index entries when mounting volumes or accessing files. When the driver processes a maliciously crafted NTFS structure, it reads memory beyond the bounds of an allocated buffer.

This out-of-bounds access exposes adjacent kernel memory contents to a controllable code path. An attacker can use the leaked data to defeat kernel address space layout randomization (KASLR) or to recover sensitive kernel objects required to complete a privilege escalation chain. The reachable code path executes in kernel mode, which is why a read-only flaw maps to high confidentiality, integrity, and availability impact in the CVSS vector.

Root Cause

The root cause is missing or insufficient bounds validation when the NTFS driver parses attacker-influenced file system metadata. The driver trusts size or offset fields embedded in the structure and uses them to index into a buffer without confirming they remain within allocated limits.

Attack Vector

The attack vector is local and requires user interaction. A typical exploitation scenario involves the victim mounting or browsing a crafted virtual hard disk (VHD/VHDX) image, removable media, or ISO file that contains malformed NTFS metadata. When the file system driver parses the structure, the out-of-bounds read fires and leaks kernel memory back to the attacker-controlled process. The attacker then chains the leak with a separate primitive to achieve full SYSTEM privileges. No prior authentication or elevated rights are required to deliver the malicious file.

No verified public exploit code is currently available. Refer to the Microsoft CVE-2025-27733 Advisory for vendor technical guidance.

Detection Methods for CVE-2025-27733

Indicators of Compromise

Unexpected mounting of VHD, VHDX, or ISO files from user download directories, email attachment paths, or removable media
Kernel-mode crashes or bug checks referencing ntfs.sys shortly after a user opens an attachment or external image
Creation of new SYSTEM-context processes spawned from user-initiated file system operations
Anomalous child processes of explorer.exe or shell handlers immediately after disk image mounts

Detection Strategies

Monitor Windows event logs for disk image mount events (Event IDs 1, 98, and related VHDMP/PartMgr entries) correlated with user sessions
Hunt for kernel crash dumps that reference NTFS parsing functions following user interaction with untrusted files
Alert on processes that map or open \\.\PhysicalDrive or VHD device objects outside of administrative tooling
Track sudden token elevation where a non-privileged process gains SYSTEM integrity without a known service path

Monitoring Recommendations

Centralize endpoint telemetry covering file system driver activity, image mounts, and integrity-level transitions
Enable PowerShell and Sysmon logging to capture commands that attach disk images, such as Mount-DiskImage and Mount-VHD
Baseline normal VHD and ISO mount activity per host and alert on deviations from administrative workflows

How to Mitigate CVE-2025-27733

Immediate Actions Required

Apply the April 2025 Microsoft security updates referenced in the Microsoft CVE-2025-27733 Advisory to all affected Windows client and server systems
Prioritize patching internet-facing terminal servers, RDP hosts, and shared workstations where local users execute untrusted content
Inventory legacy Windows Server 2008 and 2012 systems and confirm Extended Security Update (ESU) coverage before deployment

Patch Information

Microsoft released patches for CVE-2025-27733 as part of the April 2025 Patch Tuesday cycle. Updates are available through Windows Update, the Microsoft Update Catalog, and WSUS. Administrators should consult the Microsoft CVE-2025-27733 Advisory for KB article numbers specific to each supported operating system build.

Workarounds

Block users from mounting arbitrary VHD, VHDX, and ISO files through Group Policy or AppLocker rules where business needs allow
Restrict the use of removable media on sensitive endpoints via Windows Device Control policies
Quarantine email attachments containing disk image file types at the secure email gateway until patches are deployed
Enforce least-privilege user accounts so that any successful local escalation has the smallest possible blast radius

bash

# Configuration example: query installed updates to verify patch deployment
wmic qfe list brief | findstr /i "KB"
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 20