Windows Function Discovery CVE-2026-42836

Function Discovery (FD) is a Windows subsystem that abstracts the enumeration of devices and services (e.g., PnP-X, WSD, UPnP, SSDP) for applications such as Network Discovery, the device association framework, and Devices and Printers. fdwsd.dll specifically implements the Web Services on Devices (WSD) provider that handles discovery of networked peripherals like printers and scanners. The underlying weakness is CWE-362 (Concurrent Execution Using Shared Resource with Improper Synchronization, a.k.a. race condition), meaning two or more threads in the FD service access a shared object - likely a discovery handle, device list entry, or callback structure - without proper locking, creating a Time-of-Check to Time-of-Use (TOCTOU) or use-after-free style window that the attacker can leverage to corrupt state and gain code execution at the privilege level of the host service (typically LocalService/SYSTEM). No CPE strings were provided in the input, but the MSRC advisory is the authoritative product/version source.