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In early 2022, a serious security bug (CVE-2022-24494) was revealed in Microsoft Windows. This bug is known as an Elevation of Privilege Vulnerability in the Windows Ancillary Function Driver for WinSock (afd.sys). It allows attackers to gain SYSTEM-level privileges, which means they can take over affected systems.

This post will explain what the CVE is about, how it can be exploited, and why it's dangerous—using simple terms, practical code snippets, and trustworthy references.

What is the Ancillary Function Driver for WinSock?

The Ancillary Function Driver for WinSock (afd.sys) is a driver that helps Windows deal with networking operations. Many programs and services rely on this driver for communication.

Unfortunately, bugs in drivers like afd.sys are serious because drivers run with kernel-level (SYSTEM) privileges. If an attacker tricks the driver into misbehaving, they might gain the highest possible level of access in Windows.

What is CVE-2022-24494?

Microsoft describes this as an Elevation of Privilege issue (see Microsoft Security Guide). In short:

By crafting a special request, they can make the driver execute code with full SYSTEM privileges

That means malware, ransomware, or an attacker needs only to get a toe in the door (like running as a regular user) to fully compromise a Windows system!

1. Attack Vector

The vulnerability is due to improper validation of parameters in afd.sys. Attackers can send malformed requests to the driver using the DeviceIoControl function.

A simple pseudocode of how a user-mode app talks to a driver

#include <windows.h>

int main() {
    HANDLE hDevice = CreateFileA(
        "\\\\.\\AFD",
        GENERIC_READ | GENERIC_WRITE,
        , NULL, OPEN_EXISTING, , NULL);

    if (hDevice == INVALID_HANDLE_VALUE) return 1;

    // Set up your exploit input buffer - this is the tricky part,
    // must match what triggers the bug in afd.sys
    char exploitInputBuffer[128] = {}; // crafted

    DWORD bytesReturned;
    DeviceIoControl(
        hDevice,
        /* Control code goes here */,
        exploitInputBuffer,
        sizeof(exploitInputBuffer),
        NULL, ,
        &bytesReturned,
        NULL
    );

    CloseHandle(hDevice);
    return ;
}

The hardest part is, you need to know the right control code and buffer to send—security researchers reverse-engineered afd.sys to figure it out. Malicious code would craft this input to manipulate memory, causing the driver to run malicious code as SYSTEM.

2. Proof of Concept and Exploit Code

One public proof of concept (PoC) demonstrates the attack. Here's a high-level version of the exploit logic:

The attacker plants shellcode (malicious instructions) that are run as SYSTEM

Result: The attacker's program pops a new administrator command prompt!

Attackers might use shellcode like this (simplified for educational purposes)

// Example: Spawning SYSTEM command prompt
unsigned char shellcode[] = \
"\x90\x90\x90..." // NOP sled
"\xCC" // INT3 - break for debugger (real code would use syscall, etc.)
"...";

The exploit would overwrite a function pointer to point to this buffer.

Impact

- Who is affected? Any Windows machine, before patches, running supported Windows versions (Windows 7, 8, 10, 11, and Windows Server).
- How can it be abused? Local attackers, malware, ransomware—anything running as a regular user could become SYSTEM.
- How serious is it? Extremely serious, because privilege escalation enables full system compromise.

References and Further Reading

- Microsoft CVE page: CVE-2022-24494
- Exploit Details: GitHub PoC
- ZDI Technical Analysis: Zero Day Initiative Advisory
- CISA Exploited Vulnerabilities Catalog

Limit untrusted code execution. Don’t run unknown programs as an ordinary user.

- Monitor for suspicious activity. Privilege escalation attempts are often followed by other malware behaviors.

Final Notes

CVE-2022-24494 is a textbook example of why local privilege escalation bugs are a huge deal for Windows users. Even if you’re careful about online threats, just having this bug unpatched could mean complete system compromise.

If you're interested in learning more, check the references above and always stay up-to-date with the latest Windows security patches.


*This exclusive write-up is for educational purposes. Never use this information for unauthorized attacks.*

Timeline

Published on: 04/15/2022 19:15:00 UTC
Last modified on: 04/22/2022 17:20:00 UTC