In March 2025, researchers discovered a critical vulnerability in Microsoft Windows’ NTFS (New Technology File System) driver: CVE-2025-27483. This flaw allows a local, unauthorized attacker to elevate privileges on the system, potentially leading to complete control over the affected machine. In this post, we’ll break down what this bug means, how it can be exploited, and what you can do to safeguard your systems.

What is CVE-2025-27483?

CVE-2025-27483 is an “out-of-bounds read” vulnerability in the Windows NTFS driver. The bug can be triggered by an attacker with access to the local system — no administrative rights required. By crafting a specific sequence of file system operations, the attacker can trick NTFS into reading memory it shouldn’t, leading to privilege escalation.

Technical Details

The issue lies in how NTFS processes certain file system metadata. Under specific conditions, NTFS fails to properly check boundaries while traversing MFT (Master File Table) entries. This oversight allows specially crafted input to cause NTFS to read memory beyond a valid buffer — potentially exposing sensitive system data or control tokens to the attacker.

Proof-of-Concept (PoC) Example

Below is a simplified, illustrative snippet that shows how such a bug might arise. (Note: this is pseudocode for demonstration only.)

// Vulnerable NTFS driver code (simplified illustration)
NTFS_RECORD *record = get_ntfs_record(file_handle);
int index = user_controllable_value; // Not properly sanitized
char data = record->entries[index];  // Out-of-bounds read may occur here

In this scenario, the index value comes from user-controllable input (e.g., file metadata or crafted file operations) and is not validated against the array bounds, leading to reading arbitrary kernel memory. If a sensitive token or pointer is exposed, the attacker can use it to elevate their privileges.

Gaining Local Access: The attacker runs code or scripts as a local, unprivileged user.

2. Crafting Malicious Files/Structures: They create files or directories with specially crafted metadata.
3. Triggering the Vulnerability: Interacting with the file system in a way that NTFS processes these malicious objects (e.g., accessing properties, indexing).

Leaking Kernel Data: The out-of-bounds read reveals sensitive pointers or process tokens.

5. Privilege Escalation: The attacker leverages this leaked information (e.g., steals a SYSTEM token) to escalate to admin rights.

Sample Exploit Skeleton (Educational only)

import os

# Step 1: Create a file with malformed metadata (requires raw disk access)
# Step 2: Access/modify to trigger NTFS bug
# Step 3: Attempt to read leaked bytes and search for SYSTEM token

# Actual exploit code requires low-level NTFS and kernel API interaction

Note: Releasing fully functional exploit code is unethical and potentially illegal. This example is for educational awareness only.

Windows Server 2019, 2022

Any unpatched Windows system using NTFS is considered vulnerable.

Microsoft has released security updates as of March 12, 2025. Users and administrators should

- Apply Windows Updates Immediately: Microsoft Security Update Guide

References

- Microsoft Security Bulletin: CVE-2025-27483
- Windows NTFS Internals
- Original Research Article on CVE-2025-27483 *(Fictitious link for illustration)*

Takeaway

CVE-2025-27483 is a reminder that even mature code like NTFS can harbor dangerous edge case bugs. If left unpatched, these can be abused for total system compromise. Always keep your systems updated, restrict unnecessary local access, and stay informed about new security issues.

Timeline

Published on: 04/08/2025 18:15:58 UTC
Last modified on: 05/06/2025 17:03:38 UTC