Security researchers and system administrators are always on the lookout for new vulnerabilities that could put Windows environments at risk. In this post, we will take a deep dive into CVE-2022-24507, a critical elevation of privilege vulnerability found in the Windows Ancillary Function Driver for WinSock (afd.sys). We’ll explore what makes this bug dangerous, how attackers might exploit it, and include code snippets demonstrating the exploitation process. Everything is explained plainly for easier understanding.

What is the Windows Ancillary Function Driver for WinSock?

The Ancillary Function Driver for WinSock, known as afd.sys, is a core system driver responsible for networking in Windows. It handles low-level socket operations, providing kernel-mode support for Winsock functions. Because it runs in the kernel, any flaw in afd.sys can have serious system-wide consequences.

CVE-2022-24507 Vulnerability Overview

- CVE ID: CVE-2022-24507

Impact: Elevation of Privilege

- CVE Link: NIST NVD Entry

Patched in: March 2022 Windows Updates

The vulnerability allows a local attacker to execute code with SYSTEM privileges by exploiting a flaw in the way afd.sys handles certain memory operations. In particular, attackers can gain higher-level permissions and take full control of a device by executing crafted code on a target machine.

How Does the Vulnerability Work?

The bug exists due to improper validation of objects passed to the driver. A local attacker can send specially-crafted input to the driver through IOCTL calls (input/output control codes), resulting in memory corruption.

More specifically, by sending malformed data through socket APIs, a non-privileged attacker can trigger a vulnerability in afd.sys that allows them to overwrite or redirect kernel memory, typically leading to a local privilege escalation (LPE).

Open a Socket to AFD: The attacker creates a socket, which talks to afd.sys.

2. Send Malicious IOCTL: The attacker crafts a specific IOCTL request to the driver with malformed input, triggering the vulnerability.
3. Gain SYSTEM Privileges: Upon success, the attacker’s application can execute code as the SYSTEM user.

Example Code Snippet

Here’s a simplified snippet, in C, showing how an attacker might communicate with the afd.sys driver to exploit the bug. *Do not use this code for malicious purposes; it’s only for educational awareness.*

#include <winsock2.h>
#include <windows.h>
#include <stdio.h>

#define AFD_IOCTL x120bb  // Example IOCTL code

int main() {
    WSADATA wsaData;
    SOCKET s; 
    DWORD bytesReturned;

    // Initialize Winsock
    WSAStartup(MAKEWORD(2, 2), &wsaData);

    // Create a TCP socket
    s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (s == INVALID_SOCKET) {
        printf("Socket creation failed\n");
        return 1;
    }

    // Malicious buffer (crafted based on vulnerability details)
    char evilBuffer[x200] = {  };
    // Set up evilBuffer as required to trigger the bug...

    // Send IOCTL to afd.sys
    int result = WSAIoctl(
        s,
        AFD_IOCTL,
        evilBuffer,
        sizeof(evilBuffer),
        NULL,
        ,
        &bytesReturned,
        NULL,
        NULL
    );

    if (result == SOCKET_ERROR) {
        printf("WSAIoctl failed: %d\n", WSAGetLastError());
    } else {
        printf("Exploit completed, check privileges!\n");
    }

    closesocket(s);
    WSACleanup();
    return ;
}

*Note*: This is a generic template to show how one might interact with the vulnerable driver. The real exploit requires precise crafting of the buffer to trigger memory corruption.

Add, remove, or modify user accounts

This attack requires local access (a standard user account), but privilege escalation vulnerabilities like this are often chained with remote exploits for full system compromise.

Mitigation and Patch

Microsoft patched this vulnerability in March 2022.
If you have not installed Windows updates from that period or later, your system might be at risk.

Official Patch Info:

- Microsoft Security Update Guide for CVE-2022-24507

How to stay protected:

Learn More & References

- Microsoft CVE page
- NIST NVD Reference
- Windows AFD.sys documentation

Conclusion

CVE-2022-24507 is a significant Windows kernel vulnerability that underlines the danger of operating trusted code with high privileges. While Microsoft has quickly patched the hole, unpatched systems remain tempting targets. Always keep your operating system updated and practice the principle of least privilege to minimize potential damage from similar vulnerabilities.

If you’re a defender, patch promptly and stay vigilant. If you’re a researcher, use these insights responsibly to help secure the ecosystem.

Timeline

Published on: 03/09/2022 17:15:00 UTC
Last modified on: 05/23/2022 17:29:00 UTC