CVE-2026-24293: Windows WinSock Driver Privilege Escalation

CVE-2026-24293 Overview

CVE-2026-24293 is a null pointer dereference vulnerability in the Windows Ancillary Function Driver for WinSock (AFD.sys) that enables an authorized attacker to escalate privileges locally. This driver is a critical kernel-mode component responsible for handling Winsock operations, making it a high-value target for local privilege escalation attacks.

The vulnerability allows a low-privileged user to trigger a null pointer dereference condition in the AFD driver, potentially leading to arbitrary code execution with SYSTEM-level privileges. This type of vulnerability is particularly dangerous in enterprise environments where local attackers may seek to escalate from standard user accounts to full system control.

Critical Impact

Local privilege escalation to SYSTEM-level access through exploitation of the Windows Ancillary Function Driver for WinSock kernel component

Affected Products

• Windows Ancillary Function Driver for WinSock (AFD.sys)
• Windows operating systems utilizing the AFD driver
• Windows Server editions with WinSock functionality

Discovery Timeline

• 2026-03-10 - CVE-2026-24293 published to NVD
• 2026-03-11 - Last updated in NVD database

Technical Details for CVE-2026-24293

Vulnerability Analysis

This vulnerability is classified as CWE-476 (NULL Pointer Dereference) and affects the Windows Ancillary Function Driver for WinSock. The AFD driver operates at the kernel level, handling socket operations and serving as the bridge between user-mode Winsock APIs and the underlying TCP/IP stack.

When exploited, the null pointer dereference can be leveraged to corrupt kernel memory or manipulate control flow, ultimately enabling privilege escalation from a low-privileged user context to SYSTEM-level access. The local attack vector requires the attacker to have an authenticated session on the target system, but no user interaction is required to trigger the vulnerability.

Root Cause

The root cause of this vulnerability lies in improper validation of pointer references within the AFD driver's handling of certain socket operations. When specific conditions are met, the driver fails to properly check whether a pointer is valid before attempting to dereference it. This missing null check allows an attacker to craft malicious input that causes the driver to access memory at address zero or other controlled locations.

In kernel-mode exploitation scenarios, null pointer dereference vulnerabilities can be particularly severe because attackers may be able to map memory at low addresses (depending on OS mitigations) or use the resulting crash to leak kernel memory information that aids in further exploitation.

Attack Vector

The attack requires local access to the target system with at least low-level privileges. An attacker would need to execute a specially crafted application that makes specific WinSock API calls designed to trigger the vulnerable code path in the AFD driver. The exploitation typically involves:

1. Opening a socket handle through standard WinSock APIs
2. Sending crafted IOCTL requests to the AFD driver
3. Triggering the null pointer dereference condition with malformed parameters
4. Leveraging the resulting kernel memory corruption for privilege escalation

The vulnerability mechanism involves sending specially crafted requests to the AFD driver that cause it to dereference an unvalidated pointer. Technical details regarding the specific vulnerable functions and exploitation methodology can be found in the Microsoft Security Update for CVE-2026-24293.

Detection Methods for CVE-2026-24293

Indicators of Compromise

• Unexpected crashes or blue screens (BSODs) related to AFD.sys with null pointer access violations
• Suspicious process activity involving socket operations followed by privilege escalation
• Anomalous IOCTL requests targeting the AFD driver from non-standard applications
• Process token modifications indicating elevation from standard user to SYSTEM

Detection Strategies

• Monitor for unusual patterns of WinSock API calls combined with privilege escalation events
• Implement kernel-mode driver crash monitoring with focus on AFD.sys exceptions
• Deploy endpoint detection rules that correlate socket operations with subsequent privilege changes
• Use memory integrity monitoring to detect kernel memory corruption patterns

Monitoring Recommendations

• Enable Windows Event Log auditing for privilege escalation events (Event ID 4672, 4673)
• Configure crash dump analysis for any AFD.sys related kernel exceptions
• Implement behavioral analysis for processes that open socket handles then acquire elevated privileges
• Monitor for suspicious applications making high volumes of IOCTL requests to the AFD driver

How to Mitigate CVE-2026-24293

Immediate Actions Required

• Apply the latest Windows security updates from Microsoft immediately
• Restrict local access to systems to trusted users only until patches are deployed
• Enable Kernel Address Space Layout Randomization (KASLR) and other kernel hardening features
• Monitor for exploitation attempts using endpoint detection and response solutions

Patch Information

Microsoft has released a security update to address this vulnerability. Organizations should apply the patch available through Windows Update or the Microsoft Update Catalog. For detailed patch information and affected version specifics, refer to the Microsoft Security Update for CVE-2026-24293.

SentinelOne Singularity provides protection against exploitation attempts targeting this vulnerability through behavioral AI detection and real-time kernel monitoring capabilities. The platform can detect anomalous driver interactions and privilege escalation patterns associated with AFD.sys exploitation.

Workarounds

• Limit local logon privileges to reduce the attack surface for low-privileged users
• Implement application allowlisting to prevent unauthorized executables from running
• Use network segmentation to isolate high-value systems where immediate patching is not possible
• Consider temporarily restricting non-essential WinSock functionality in highly sensitive environments pending patch deployment

Organizations should prioritize patching as the primary mitigation strategy, as workarounds may impact system functionality and do not fully address the underlying vulnerability.