Preface: Any standard machine learning framework running on Windows (such as PyTorch, TensorFlow, or ML.NET) interacts indirectly with afd.sys when performing network tasks (such as downloading datasets, communicating with distributed nodes, or querying cloud APIs).

Background: afd[.]sys is the Windows Accessibility driver for WinSock. It is a core kernel-mode driver in the Windows operating system, responsible for managing network socket operations and acting as a bridge between user-mode network applications and the system stack.

The Ancillary Function Driver for WinSock (afd[.]sys) is a fundamental kernel-mode driver in Windows. It is responsible for handling all standard network socket connections via the Windows Sockets API (Winsock). Because it is a system-wide networking driver, any application that connects to the internet or a local network relies on it.

How the Communication Pipeline Works?

1. The Trigger (User Mode): Applications cannot talk directly to the network hardware or kernel memory. When an application wants to open a socket, it calls standard functions inside ws2_32[.]dll.

2. The Bridge (DeviceIoControl): The Winsock DLL translates that application request into a specialized Windows system call using the DeviceIoControl() API. This function packages:

•               An IOCTL Code: A specific command ID telling the driver exactly what network operation to perform.

•               Input/Output Buffers: Pointers to the memory blocks containing the data to send or spaces to hold incoming data.

3. The Gateway (afd[.]sys): The execution crosses the secure boundary into Kernel Mode. The request lands directly in afd[.]sys. Because it runs inside the kernel, afd.sys has absolute power over system memory and execution.

Vulnerability details: Use after free in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.

Official announcement: Please refer to the link for details – https://nvd.nist.gov/vuln/detail/CVE-2026-68820