CVE-2026-50462: Windows WinSock Privilege Escalation Flaw

CVE-2026-50462 Overview

CVE-2026-50462 is a local privilege escalation vulnerability in the Windows Ancillary Function Driver for WinSock (afd.sys). The flaw allows an authorized attacker with low privileges to elevate to higher privileges on an affected Windows system. The root cause is external control of a file name or path, classified under [CWE-73]. Microsoft published the advisory on July 14, 2026, and no public proof-of-concept exploit is currently available.

Critical Impact
An authenticated local attacker can leverage the driver flaw to gain elevated privileges, compromising the confidentiality, integrity, and availability of the affected host.

Affected Products

Microsoft Windows (Ancillary Function Driver for WinSock component)
Specific affected Windows versions: refer to the Microsoft Security Update Guide
Both client and server Windows editions shipping afd.sys are potentially in scope

Discovery Timeline

2026-07-14 - CVE-2026-50462 published to NVD
2026-07-15 - Last updated in NVD database

Technical Details for CVE-2026-50462

Vulnerability Analysis

The Ancillary Function Driver for WinSock (afd.sys) is a kernel-mode driver that provides the WinSock kernel interface for user-mode socket operations. The driver operates in kernel context and processes I/O requests from unprivileged user processes. Any flaw in path handling within this component crosses a security boundary between user and kernel mode.

CVE-2026-50462 arises when the driver constructs or resolves a file name or path using input influenced by an unprivileged caller. Because the driver runs as NT AUTHORITY\SYSTEM, an attacker can direct the driver to act on a file resource that the attacker would not otherwise be authorized to access. Successful exploitation results in local privilege escalation to SYSTEM.

Root Cause

The underlying weakness is [CWE-73]: External Control of File Name or Path. The driver accepts attacker-influenced path data without adequately validating that the resolved target lies within a permitted namespace. This enables the attacker to redirect a privileged file operation to a location of their choosing.

Attack Vector

Exploitation requires local access and low-privileged authenticated execution on the target. The attacker interacts with afd.sys through standard socket or DeviceIoControl calls, supplying crafted path input. No user interaction is required beyond the attacker running their own code. Refer to the Microsoft Security Update for CVE-2026-50462 for vendor-provided technical details. No verified public exploit code is available at the time of writing.

Detection Methods for CVE-2026-50462

Indicators of Compromise

Unexpected creation, modification, or deletion of files in privileged locations by unprivileged user processes
Anomalous DeviceIoControl calls issued against the \Device\Afd device from non-standard binaries
New processes spawned as SYSTEM whose parent is a standard user-context process
Loading of unsigned or unexpected modules into processes interacting with WinSock kernel interfaces

Detection Strategies

Monitor kernel object access patterns to afd.sys for anomalous handle open sequences from low-integrity processes
Alert on privilege elevation events (Windows Event ID 4672, 4688) tied to processes originating from user sessions without administrative context
Correlate socket-related syscalls with subsequent file operations in sensitive directories such as C:\Windows\System32 or C:\Windows\Temp

Monitoring Recommendations

Enable and forward Sysmon Event IDs 1, 11, and 13 to detect anomalous process, file, and registry activity following socket API usage
Baseline normal afd.sys interaction per host role and alert on deviations
Track patch compliance for the July 2026 Windows security updates across the estate

How to Mitigate CVE-2026-50462

Immediate Actions Required

Apply the Microsoft security update referenced in the MSRC advisory for CVE-2026-50462 to all affected Windows systems
Prioritize patching on multi-user systems such as Remote Desktop Session Hosts, VDI infrastructure, and shared workstations
Restrict local logon rights and remove unnecessary interactive accounts on sensitive servers

Patch Information

Microsoft addressed CVE-2026-50462 in the July 2026 security update cycle. The corrected afd.sys binary validates path input before performing privileged file operations. Consult the Microsoft Security Update Guide for the specific KB articles and version numbers that apply to each affected Windows release.

Workarounds

No official vendor workaround is published; patch installation is the supported remediation path
Reduce exposure by enforcing least privilege and blocking execution of untrusted binaries via application control policies such as Windows Defender Application Control (WDAC) or AppLocker
Segment and monitor systems that cannot be immediately patched, and limit which users can execute arbitrary code on them

bash

# Verify installation of the July 2026 cumulative update on Windows
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 10

# Check the current version of afd.sys against the vendor-published fixed version
Get-Item C:\Windows\System32\drivers\afd.sys | Select-Object VersionInfo