Executive brief
A security vulnerability exists in a core Windows networking component responsible for handling socket connections. An attacker who already has basic access to a computer could exploit this flaw to gain full administrative control over the system. This could allow them to bypass security restrictions, access sensitive data, or install malicious software.
Technical details
A type confusion vulnerability exists in the Windows Ancillary Function Driver (afd.sys), which serves as the kernel-mode interface for WinSock. The flaw stems from the driver incorrectly processing resources using incompatible types, or potentially through external control of file paths during socket operations. An attacker with low-privileged local access can exploit this by sending specially crafted I/O control (IOCTL) requests to the driver. Successful exploitation allows the attacker to execute code with SYSTEM privileges, effectively gaining full control of the affected host. Microsoft has released security updates to address this issue across supported versions of Windows and Windows Server.
Affected products
- Microsoft Windows 10 21H2, 22H2
- Microsoft Windows 11 23H2, 24H2, 25H2, 26H1
- Microsoft Windows Server 2022 Standard, 23H2
- Microsoft Windows Server 2025 All versions
Timeline
- 2026-05-12: disclosed
- 2026-05-12: advisory