CVE-2025-32709

What it actually does

CVE-2025-32709 is a local privilege escalation vulnerability in the Windows Ancillary Function Driver for WinSock, afd.sys. An authenticated attacker with local code execution can trigger the vulnerable kernel driver path and cause unsafe kernel behavior that can be weaponized to elevate privileges. Successful exploitation can allow the attacker to execute code with high-integrity or SYSTEM-level privileges, giving them full control over the affected Windows host, including the ability to read or modify protected data, disable security tooling, install persistence, and move laterally using stolen credentials.

Why it matters to the business

This vulnerability is high priority because it is listed in CISA KEV and has been observed exploited in the wild, with a federal remediation deadline of 2025-06-03 that has already passed. Although it requires local access, it is valuable to attackers after an initial foothold because it can turn a low-privileged compromise into full host compromise. Affected systems include a broad range of Windows client and server versions, including Windows 10, Windows 11, Windows Server 2008 through Server 2025, so exposure may be widespread across workstations, servers, VDI, and legacy systems. Business consequences include ransomware enablement, credential theft, endpoint security disablement, data exposure, service disruption, and increased likelihood of domain-wide compromise if exploited on privileged or server systems.

How an attack unfolds

An attacker first obtains authenticated local execution on a Windows system, commonly through phishing, malware, exploitation of an application, abuse of valid credentials, or a web shell on a Windows server. From that foothold, the attacker runs exploit code that interacts with the Windows Ancillary Function Driver for WinSock through local kernel interfaces exposed by afd.sys. The exploit triggers the vulnerable code path and manipulates the resulting kernel condition to gain elevated execution. Once elevated, the attacker typically spawns a SYSTEM shell or injects into a privileged process, disables or tampers with endpoint defenses, dumps credentials, installs persistence such as services or scheduled tasks, and uses the host as a staging point for lateral movement. The vulnerability is not generally an initial remote entry point by itself, but it is highly useful in real intrusions because it removes local privilege barriers after compromise.

How to fix it

Apply the Microsoft security updates that address CVE-2025-32709 for all affected Windows versions. Because no exact fixed build list was provided, use the May 2025 Microsoft security update baseline or later cumulative updates for each supported Windows release, including Windows 10, Windows 11, Windows Server 2016, 2019, 2022, 2022 23H2, and 2025. For Windows Server 2008 and Windows Server 2012, ensure the appropriate Extended Security Updates are applied if eligible; otherwise migrate or isolate unsupported systems. Prioritize internet-facing Windows servers, systems used by administrators, domain-joined workstations, VDI pools, jump hosts, and any servers where local compromise could expose high-value credentials. If immediate patching is not possible, reduce risk by limiting interactive logon rights, removing unnecessary local administrator access, enforcing least privilege, strengthening EDR prevention policies, blocking untrusted executable execution, and isolating legacy systems. There is no reliable configuration-only mitigation that provides the same protection as applying the vendor update.

How to confirm the fix worked

Confirm that each affected Windows host has installed the relevant Microsoft cumulative security update from May 2025 or later. Validate through enterprise patch management, Windows Update history, Microsoft Update Compliance, vulnerability scanners, or PowerShell inventory of installed hotfixes and OS build numbers. On representative systems, confirm the afd.sys file version and timestamp align with the patched Microsoft release for that OS build. Reboot systems after patching where required, because kernel driver fixes are not fully effective until the updated driver is loaded. Re-scan systems after remediation and verify that no vulnerable Windows 10, Windows 11, or Windows Server builds remain. For unsupported systems, document compensating controls and confirm isolation or migration plans.

Typical attack path

1. Gain initial authenticated local code execution on an affected Windows workstation or server.
2. Transfer or stage a local privilege escalation exploit targeting afd.sys.
3. Execute the exploit from a low-privileged user context.
4. Trigger the vulnerable Windows Ancillary Function Driver for WinSock code path.
5. Obtain elevated privileges, commonly SYSTEM-level execution.
6. Launch a privileged shell, service, scheduled task, or injected process.
7. Disable security controls, dump credentials, or access protected files.
8. Establish persistence and move laterally to additional systems.

How to detect it

Exploitation of this kernel privilege escalation vulnerability may not leave a dedicated Windows event that names the vulnerability, so detection should focus on behavioral evidence before and after elevation. Review EDR, Sysmon, Windows Security, System, PowerShell, Defender, and service control logs for low-privileged user activity followed closely by SYSTEM-level execution, new service creation, suspicious scheduled tasks, credential dumping, LSASS access, security tool tampering, or lateral movement. Useful Windows events include Security 4688 for process creation, 4672 for special privileges assigned, 4624 for logon context changes, 4697 or System 7045 for service installation, 4698 for scheduled task creation, and Defender or EDR alerts for exploit behavior or credential theft. Check crash telemetry and Windows Error Reporting for unusual kernel crashes involving afd.sys, although successful exploitation may not crash the system. For forensic review, examine Prefetch, Amcache, ShimCache, SRUM, PowerShell logs, EDR file/process telemetry, and memory captures for exploit binaries or processes interacting with AFD before privilege escalation. Because this CVE is KEV-listed and actively exploited, treat detections involving afd.sys exploit attempts, unexplained SYSTEM shells, or post-exploitation behavior on unpatched hosts as high confidence compromise leads.

• afd.sys
• \Device\Afd
• Ancillary Function Driver for WinSock
• Microsoft-Windows-WER-SystemErrorReporting
• BugCheck
• SYSTEM
• Event ID 7045
• Event ID 4697
• Event ID 4698
• Event ID 4672
• Event ID 4688
• SeDebugPrivilege
• lsass.exe
• comsvcs.dll
• MiniDump
• procdump.exe
• rundll32.exe C:\Windows\System32\comsvcs.dll, MiniDump
• sc.exe create
• schtasks.exe /create
• powershell.exe -ExecutionPolicy Bypass
• cmd.exe /c whoami /priv

What your security team should do

• Treat this as urgent despite the modest EPSS score because it is CISA KEV-listed and has confirmed exploitation in the wild.
• Prioritize patching systems that are exposed to untrusted users, run server workloads, store credentials, or are used for administration.
• Hunt for signs of recent local privilege escalation followed by SYSTEM-level process execution, credential dumping, service creation, or endpoint defense tampering.
• Review EDR telemetry for low-privileged processes spawning elevated shells, command interpreters, scripting engines, or suspicious child processes.
• Restrict local logon, RDP, and administrative rights to reduce the number of users who can reach the local precondition for exploitation.
• Ensure tamper protection, attack surface reduction rules, credential theft protections, and application control policies are enabled where feasible.
• Investigate any unpatched host that also shows malware, web shell, suspicious PowerShell, credential access, or lateral movement activity as potentially compromised.
• For legacy Windows Server 2008 and 2012 assets, accelerate migration, isolate them from general network access, or ensure Extended Security Updates are actually applied.