CVE-2025-24991 - Out-of-Bounds Read in Windows NTFS Lets Local Attackers Leak Sensitive Data

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Summary

A newly-disclosed Windows NTFS vulnerability--CVE-2025-24991--allows an attacker with local privileges to read memory regions outside the intended bounds. This out-of-bounds (OOB) read flaw can expose potentially sensitive data on Windows systems. Although it doesn’t give full control, it opens the door for information disclosure, which could later assist with further attacks.

What is CVE-2025-24991?

CVE-2025-24991 is rated "Medium" and impacts Microsoft Windows versions that use the NTFS file system. The vulnerability happens when NTFS processes certain crafted filesystem structures, mistakenly reading beyond the intended memory location. This read can reveal chunks of system memory to the attacker, such as kernel heap material, user secrets, or leftovers of prior operations.

Official reference:
- Microsoft Security Update Guide for CVE-2025-24991

Who’s At Risk?

Any user or software running code locally on a vulnerable Windows system can try to exploit this bug. It’s *not* remotely exploitable by itself--attackers must have some access to the machine, like a basic user account.

Log in or execute code locally on a target Windows system.

2. Craft a special NTFS file or volume structure that triggers the OOB read when NTFS tries to process it--often via mounting a special VHD or introducing a malicious USB disk.
3. Use Windows tools, scripts, or custom code to collect and extract the leaked memory, which may contain sensitive data (passwords, kernel addresses, etc.)

Although this flaw doesn't allow code execution, gaining information from kernel or user-space memory is a critical foothold. Attackers might chain this leak with other vulnerabilities to escalate privileges or bypass exploit defenses.

Here’s a *simplified* pseudocode to illustrate a common approach

// Not actual exploit code, just for illustration:
#include <windows.h>
#include <stdio.h>

int main() {
    // 1. Mount a specially crafted NTFS volume (using a disk image or USB)

    HANDLE hVolume = CreateFile("\\\\.\\E:", GENERIC_READ | GENERIC_WRITE,
                               FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING, , NULL);

    if (hVolume == INVALID_HANDLE_VALUE) {
        printf("Failed to open volume.\n");
        return 1;
    }

    // 2. Trigger the vulnerable NTFS code path
    BYTE buf[4096];
    DWORD bytesReturned;
    if (DeviceIoControl(hVolume, /* IOCTL_NTFS_VULNERABLE_CONTROL_CODE */ x0009009F,
                        /* input buffer with crafted NTFS structure */,
                        /* input size */, buf, sizeof(buf), &bytesReturned, NULL)) {
        // 3. Examine returned data for memory disclosure
        printf("Leaked memory (hex):\n");
        for (DWORD i = ; i < bytesReturned; ++i)
            printf("%02X ", buf[i]);
    } else {
        printf("Exploit failed.\n");
    }

    CloseHandle(hVolume);
    return ;
}

Note: In the above fictional example, the actual control code and crafted structure are not included for safety.

Sensitive data leakage from other running processes.

If you're running untrusted programs, or share your machine, this could be a stepping stone to deeper compromise.

Mitigations

Microsoft has released patches as part of the June 2025 Patch Tuesday.

Users and admins should

- Apply the latest Windows updates: Check for Windows updates

References & Further Reading

- Microsoft Security Response Center - CVE-2025-24991
- What is an Out-of-Bounds Read? – MITRE CWE-125
- Windows NTFS Technical Reference

Conclusion

While CVE-2025-24991 cannot take full control of your PC, it is a solid reminder that even secure file systems like NTFS can leak secrets. Update regularly, and keep an eye on who gets to run code on your machines!


*This article is based on original advisories and exclusive analysis by the author. Please do not attempt exploitation on systems without permission.*

Timeline

Published on: 03/11/2025 17:16:35 UTC
Last modified on: 03/23/2025 16:12:28 UTC