CVE-2025-27741 Overview
CVE-2025-27741 is an out-of-bounds read vulnerability in the Windows New Technology File System (NTFS) driver. The flaw allows a local, unauthenticated attacker to elevate privileges after convincing a user to perform an action, such as opening a crafted file or mounting a specially crafted virtual disk. Successful exploitation grants the attacker high impact on confidentiality, integrity, and availability of the affected host. Microsoft has published a security update addressing the issue across supported Windows client and server releases, including Windows 10 (1507, 1607, 1809) and Windows Server 2008 through 2019.
Critical Impact
Local privilege escalation to SYSTEM through a crafted NTFS structure, enabling full host compromise from a low-privilege user context.
Affected Products
- Microsoft Windows 10 versions 1507, 1607, and 1809 (x86 and x64)
- Microsoft Windows Server 2008 SP2 and Windows Server 2008 R2 SP1
- Microsoft Windows Server 2012, 2012 R2, 2016, and 2019
Discovery Timeline
- 2025-04-08 - CVE-2025-27741 published to the National Vulnerability Database
- 2026-06-17 - Last updated in the NVD database
Technical Details for CVE-2025-27741
Vulnerability Analysis
The vulnerability is an out-of-bounds read [CWE-125] in the Windows NTFS driver. When NTFS parses attacker-controlled on-disk metadata, it reads memory beyond the intended bounds of an internal buffer. The disclosed memory contents can include kernel pointers, security tokens, or adjacent object data that assist an attacker in defeating kernel address space layout randomization (KASLR) and constructing a follow-on privilege escalation primitive.
Exploitation requires local access and user interaction, typically achieved by mounting a specially crafted virtual hard disk (VHD or VHDX) or opening a malicious file on a rogue NTFS volume. Once the driver processes the malformed structure, the leaked data is used to elevate privileges from a standard user to SYSTEM. The exploit prediction scoring system rates the exploitation probability at 0.724%.
Root Cause
The root cause is missing or insufficient bounds validation when NTFS parses length-prefixed on-disk attributes. A crafted attribute record with an oversized or malformed size field causes the driver to read past the allocated buffer during metadata processing, disclosing kernel memory to the calling context.
Attack Vector
The attack vector is local. An attacker with the ability to log in interactively or execute code as a standard user delivers a crafted NTFS image, often packaged as a VHDX file. When the image is mounted, the NTFS driver parses attacker-controlled metadata in kernel mode. The leaked kernel information is chained with a secondary write primitive to complete the privilege escalation. Verified public proof-of-concept code for CVE-2025-27741 is not available at the time of writing.
Detection Methods for CVE-2025-27741
Indicators of Compromise
- Unexpected mounting of VHD or VHDX files by non-administrative users, particularly from user-writable directories such as %TEMP% or %APPDATA%.
- Kernel bugchecks referencing ntfs.sys or crashes in NtfsReadAttribute shortly after a user opens an unfamiliar disk image.
- Local processes spawning SYSTEM-level children without a corresponding legitimate service or scheduled task.
Detection Strategies
- Monitor for creation and mounting of disk image files by standard users, correlating file writes with subsequent Mount-DiskImage or PowerShell VHD attach activity.
- Alert on child processes of winlogon.exe, services.exe, or lsass.exe that originate from unexpected parent chains following a mount event.
- Hunt for anomalous access-token duplication or SeDebugPrivilege acquisition by processes launched from a user session immediately after NTFS driver activity.
Monitoring Recommendations
- Enable Windows Defender Application Control or attack surface reduction rules to block untrusted VHDX mounting by standard users.
- Ingest kernel crash telemetry (WER and Minidump events) into a central log store and alert on repeat faults in ntfs.sys.
- Track patch compliance for the April 2025 Microsoft security rollup across all endpoints and servers running affected Windows builds.
How to Mitigate CVE-2025-27741
Immediate Actions Required
- Deploy the Microsoft security update referenced in the Microsoft Security Update CVE-2025-27741 advisory to all affected Windows client and server systems.
- Prioritize patching multi-user systems, jump hosts, and terminal servers where local privilege escalation would enable lateral movement.
- Restrict the ability of standard users to mount arbitrary VHD or VHDX images via Group Policy and least-privilege enforcement.
Patch Information
Microsoft released fixes as part of the April 2025 Patch Tuesday cycle. Consult the Microsoft Security Update CVE-2025-27741 advisory for the specific knowledge base article and update package matching each affected Windows build.
Workarounds
- Block delivery of .vhd, .vhdx, and .iso attachments at the email gateway and web proxy for standard users where feasible.
- Remove the Backup Operators and disk-image mounting rights from non-administrative accounts until patches are applied.
- Apply application allowlisting to prevent execution of untrusted binaries from removable or mounted volumes.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
