CVE-2024-26177 - Windows Kernel Information Disclosure Vulnerability Explained

In February 2024, Microsoft addressed an important security vulnerability in the Windows kernel known as CVE-2024-26177. This flaw enables local attackers to steal sensitive information, which can further aid in exploiting a system or bypassing security features. In this post, we’ll break down what CVE-2024-26177 is, how attackers could use it, walk through some code examples, and show you how to protect your systems. All information is provided in plain, straightforward language for security beginners and enthusiasts alike.

What is CVE-2024-26177?

CVE-2024-26177 is a security flaw found in the Windows kernel – the core component of all Windows operating systems. The vulnerability allows a local attacker (someone who already has access to the computer, even as a basic user) to access parts of the computer’s memory that should normally be hidden. This leak can give away information that helps attackers find and exploit additional vulnerabilities or bypass various protections.

Why Does It Matter?

While information disclosure doesn’t sound as severe as full remote code execution, it’s an essential step for many attacks:
- Attackers may read kernel memory to discover secrets such as addresses, tokens, or cryptographic keys.

What Was Wrong

The vulnerability lies in the way certain Windows kernel drivers handle memory. Specifically, the kernel sometimes allocates memory for returning results to user-mode applications, but doesn’t always zero out (clear) this memory before sending it back. As a result, leftover data from previous kernel operations can be exposed.

Microsoft’s official description

> An information disclosure vulnerability exists when the Windows kernel improperly discloses the contents of its memory.

Windows Server 2016, 2019, 2022

(See Microsoft’s advisory for the full list.)

Sample Exploit Code

Here's a simplified C code snippet to demonstrate how such information leaks are usually detected. (NOTE: This is generic; Microsoft has not publicly disclosed the exact function name or driver involved. But typical proof-of-concept (PoC) exploits look like this.)

#include <windows.h>
#include <stdio.h>

#define BUFFER_SIZE x100

int main() {
    BYTE buffer[BUFFER_SIZE] = {};
    DWORD bytesReturned;

    // Example of a suspicious DeviceIoControl call
    HANDLE hDevice = CreateFile(L"\\\\.\\VulnerableDriver", 
        GENERIC_READ | GENERIC_WRITE, , NULL, OPEN_EXISTING, , NULL);

    if (hDevice == INVALID_HANDLE_VALUE) {
        printf("Could not open handle: %lu\n", GetLastError());
        return 1;
    }

    // Replace IOCTL_CODE with the actual code as determined by reverse engineering
    DWORD IOCTL_CODE = x222003;

    BOOL result = DeviceIoControl(hDevice, IOCTL_CODE, 
        NULL, , buffer, BUFFER_SIZE, &bytesReturned, NULL);

    if (result) {
        printf("Data returned from kernel:\n");
        for(int i = ; i < bytesReturned; i++) {
            printf("%02x ", buffer[i]);
        }
        printf("\n");
    } else {
        printf("DeviceIoControl failed.\n");
    }

    CloseHandle(hDevice);
    return ;
}

> Note: This is not a weaponized exploit, just an outline of the type of leak at play. It demonstrates that a poorly written driver can accidentally return leftover kernel data to userland.

Real-World Exploitation

- Who can attack? Someone who already has access to the target PC (locally or via a compromised low-privileged account).
- What can be stolen? Fragments of kernel memory that could include process tokens, cryptographic secrets, pointer addresses, etc.
- Can this bug be chained? Yes! Attackers often combine info leaks like CVE-2024-26177 with other kernel bugs leading to privilege escalation or full system compromise.

How To Protect Your System

1. Apply Windows Updates: The best and only real fix is to install Microsoft’s February 2024 cumulative updates, as this plugs the hole at the OS level.
- CVE-2024-26177 update info from Microsoft
- Microsoft Patch Tuesday, Feb 2024 summary (BleepingComputer)

References

- Microsoft official advisory for CVE-2024-26177
- Zero Day Initiative: February 2024 Patch Analysis
- RedCanary: How attackers use kernel bugs
- Sample PoC for similar information disclosure bugs (Educational use only!)

Conclusion

CVE-2024-26177 is a reminder that even “just” information disclosure in the Windows kernel can be a vital stepping-stone for attackers. If exploited, it could help an attacker gain full control over your system or evade security tools. The fix is simple: keep your devices up to date, and be cautious about who can run code on your machines. Stay safe!

Let us know in the comments if you need more help understanding or patching this vulnerability.

Timeline

Published on: 03/12/2024 17:15:57 UTC
Last modified on: 03/12/2024 17:46:17 UTC