*Published: 2024-07-11*

Intro

A new security issue has surfaced in Microsoft Windows involving the NTFS file system, tracked as CVE-2025-27742. This flaw, an "out-of-bounds read," can allow a local attacker to steal sensitive files—even if they're not supposed to have access. Let's break down how this problem works, why it matters, and what you can do to stay safe.

What is an "Out-of-Bounds Read?"

Basically, an "out-of-bounds read" means a program is tricked into reading memory it shouldn't read. If the attacker can control the input (like a corrupted file or crafted filesystem), they might get the program to spit out information from outside the normal boundaries—a hacker's way of peeking behind doors that should be locked.

The NTFS Flaw (CVE-2025-27742) in Detail

The Windows NTFS (New Technology File System) is the backbone of file storage on Windows computers. The vulnerability happens when NTFS processes certain metadata, file attributes, or file system structures in a way that fails to check if it's reading safe areas in memory.

Impact: This doesn't let someone take over your computer or run code as you, but—if they can run basic commands on your system (like a standard user or a sneaky piece of malware)—they can trick Windows into giving up info stored nearby in memory. That info could be file contents, encryption keys, cached passwords, or more.

Who Can Be Attacked?

An attacker needs local access (they must have an account on the computer or run a program there). This is *not* something that can be triggered remotely, over the internet.

Example Exploit: How It Might Look

For security and legal reasons, we won't show full "weaponized" code, but here's an example of how a researcher might demonstrate the info leak on a vulnerable system:

// Pseudo C code - Research demo only
#include <windows.h>
#include <stdio.h>

int main() {
    // Open a handle to a file on NTFS partition
    HANDLE hFile = CreateFile("C:\\test.txt",
        GENERIC_READ, FILE_SHARE_READ, NULL,
        OPEN_EXISTING, , NULL);
    if (hFile == INVALID_HANDLE_VALUE) {
        printf("Unable to open file.\n");
        return 1;
    }

    char buffer[512] = {};
    DWORD bytesRead;

    // Intentionally read beyond the end of file
    // (In real exploit, this may require special file attributes or crafted files)
    SetFilePointer(hFile, 1024, NULL, FILE_BEGIN);
    if (ReadFile(hFile, buffer, sizeof(buffer), &bytesRead, NULL)) {
        printf("Leaked data:\n%.*s\n", bytesRead, buffer);
    } else {
        printf("Read failed.\n");
    }

    CloseHandle(hFile);
    return ;
}

*In real-world exploits, the attacker would use special methods to coax NTFS into leaking chunks of memory that belong to other files or system secrets.*

References and More Reading

- Microsoft Security Advisory *(Official CVE entry, patches when available)*
- NIST NVD Entry
- NTFS Internals (Wikipedia)
- Out-of-Bounds Reading Explained

Limit access: Don’t give local access to people or programs you do not trust.

- Use strong antivirus/endpoint protection to limit malware on your machine.

Final Thoughts

CVE-2025-27742 is a great reminder: Even mature, critical parts of the Windows OS like NTFS can have hidden bugs. Local exploits like this might not make the news like big internet worms—but they’re favorites for advanced attackers and insiders hunting for sensitive info.

Keep your systems updated, practice good security hygiene, and watch for bulletins from Microsoft.

Stay safe out there!

*Authored for researchers and sysadmins by AI, exclusive to this publication. For responsible research use only.*

Timeline

Published on: 04/08/2025 18:16:03 UTC
Last modified on: 04/30/2025 17:13:44 UTC