CVE-2026-68820: Windows WinSock (afd.sys) UAF Mitigation

This repository contains a conceptual patch demonstrating the mitigation for CVE-2026-68820, a critical Use-After-Free (UAF) vulnerability in the Windows Ancillary Function Driver for WinSock (afd.sys).

Active exploitation of this flaw allows a local, authenticated attacker to trigger a race condition, hijack execution flow, and escalate to SYSTEM privileges.

The Root Cause

The vulnerability stems from improper lifetime management of socket objects during the teardown phase. In the vulnerable state, afd.sys frees a context buffer but fails to immediately nullify the pointer. If a concurrent thread attempts to access the socket state during this window, it accesses freed memory (UAF).

Patch Architecture

This patch introduces a deterministic lifetime management model:

1. Thread Synchronization: Implements KeAcquireSpinLock to ensure mutual exclusion during socket destruction.
2. Nullify-Before-Free: Captures the dangling pointer, explicitly nullifies the structure member (Socket->ContextBuffer = NULL), and then frees the memory.
3. Safe Reference Counting: Utilizes InterlockedDecrement to ensure the parent object is only destroyed when all references are dropped.

Disclaimer

Windows is a closed-source operating system. This code is an educational representation of the exact logical structures and Windows Driver Model (WDM) API calls required to remediate the race condition in the kernel pool.

License

MIT License