CVE-2023-21768: 
vulnerability analysis and mitigation

The Windows Ancillary Function Driver (AFD) for WinSock vulnerability (CVE-2023-21768) is an elevation of privilege vulnerability that affects Windows Server 2022 and Windows 11 22H2. This vulnerability was disclosed in December 2022 and allows attackers with valid system access to execute arbitrary code with elevated privileges (SentinelOne).

The vulnerability exists in the AFD driver, which is a kernel-mode driver supporting WinSock for managing network sockets and communication channels. The issue specifically relates to how the AFD driver handles user-mode input/output (I/O) operations. An attacker can exploit this by sending a malicious input/output control (IOCTL) request to the AFD driver, potentially triggering a buffer overflow condition that enables arbitrary code execution with elevated privileges. The vulnerability has been assigned a CVSS v3.1 base score of 7.8 (High) with the vector string CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (NVD).

Successful exploitation of CVE-2023-21768 enables attackers to run arbitrary code in kernel mode, granting them the ability to install programs, view, modify, or delete data, and create new accounts with full user rights. The attacker can seize privilege tokens from high-privilege processes and apply them to processes of their choosing, potentially leading to complete system compromise (SentinelOne).

As a temporary mitigation measure until a security patch is available, Microsoft recommends disabling the AFD driver. However, this workaround may impact the functionality of Winsock and other network-related applications, so it should be considered a temporary solution (SentinelOne).