CVE-2025-53718 Overview
CVE-2025-53718 is a use-after-free vulnerability [CWE-416] in the Windows Ancillary Function Driver for WinSock (afd.sys). The flaw allows an authenticated local attacker to elevate privileges on affected Windows systems. Microsoft published the advisory on August 12, 2025, covering Windows 10, Windows 11, and Windows Server editions from 2008 through 2025.
Successful exploitation grants SYSTEM-level privileges, enabling full control of the compromised host. Attack complexity is high, but exploitation requires only low-privileged local access with no user interaction.
Critical Impact
An authorized local attacker can escalate to SYSTEM privileges on any supported Windows version, compromising confidentiality, integrity, and availability of the host.
Affected Products
- Microsoft Windows 10 (1507, 1607, 1809, 21H2, 22H2)
- Microsoft Windows 11 (22H2, 23H2, 24H2)
- Microsoft Windows Server 2008, 2012, 2016, 2019, 2022, 2022 23H2, and 2025
Discovery Timeline
- 2025-08-12 - CVE-2025-53718 published to NVD and Microsoft releases security update
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-53718
Vulnerability Analysis
The Ancillary Function Driver for WinSock (afd.sys) is a kernel-mode driver that provides the interface between user-mode Winsock APIs and the underlying TCP/IP stack. Any local process can issue I/O control (IOCTL) requests to \Device\Afd, which makes the driver a recurring target for local privilege escalation research.
CVE-2025-53718 is a use-after-free condition in afd.sys. Because the driver runs in kernel context, dereferencing a freed object can be steered into arbitrary kernel memory manipulation. An attacker who controls the timing and layout of the freed allocation can hijack kernel execution flow and run code with SYSTEM privileges.
Root Cause
The root cause is improper object lifetime management within afd.sys. A kernel object is freed while another code path retains a dangling reference to it. Under the right conditions, a subsequent operation dereferences the stale pointer after the underlying memory has been reallocated with attacker-controlled data.
Attack Vector
Exploitation requires an authenticated local user to execute a purpose-built binary. The attacker issues a crafted sequence of Winsock or direct IOCTL calls against \Device\Afd to trigger the race that leads to the dangling reference. High attack complexity reflects the timing dependencies inherent in reliably winning the race and grooming the kernel pool.
The vulnerability is not remotely exploitable. It is typically chained after initial access, for example following credential theft, phishing, or exploitation of a browser or productivity application, to escape a low-privileged context.
No public proof-of-concept exploit is currently listed for CVE-2025-53718, and the vulnerability is not on the CISA Known Exploited Vulnerabilities catalog at the time of writing. Technical details are described in the Microsoft Security Update CVE-2025-53718 advisory.
Detection Methods for CVE-2025-53718
Indicators of Compromise
- Unexpected user-mode processes opening handles to \Device\Afd followed by anomalous IOCTL patterns.
- Creation of new SYSTEM-level processes spawned from a medium- or low-integrity parent process.
- Kernel bugchecks or unexpected reboots referencing afd.sys on hosts prior to patching.
- Loading of unsigned or previously unseen binaries by standard users shortly before privilege changes.
Detection Strategies
- Alert on processes performing rapid, repetitive DeviceIoControl calls against AFD control codes from non-standard binaries.
- Correlate token manipulation events (Sysmon Event ID 1 with SYSTEM integrity from a non-service parent) with the originating user session.
- Hunt for parent-child anomalies where a standard user process suddenly launches children as NT AUTHORITY\SYSTEM.
Monitoring Recommendations
- Enable Windows kernel-mode driver auditing and forward Sysmon telemetry to a central data lake for retrospective hunting.
- Baseline normal AFD IOCTL usage per host role and alert on outliers, particularly on servers and jump hosts.
- Monitor for post-exploitation activity such as LSASS access, Defender tampering, and creation of scheduled tasks under SYSTEM.
How to Mitigate CVE-2025-53718
Immediate Actions Required
- Apply the August 2025 Microsoft security update that addresses CVE-2025-53718 across all affected Windows and Windows Server versions.
- Prioritize patching of multi-user systems, RDP jump hosts, VDI infrastructure, and terminal servers where low-privileged users can execute code.
- Audit local administrator group membership and remove standing privileges that could amplify chained attacks.
Patch Information
Microsoft released fixes for CVE-2025-53718 on August 12, 2025 as part of the monthly security update cycle. Refer to the Microsoft Security Update CVE-2025-53718 advisory for the specific KB article associated with each supported Windows and Windows Server build.
Workarounds
- No official workaround is published by Microsoft; patching is the required remediation.
- Restrict interactive logon and local code execution rights for untrusted users to limit access to the vulnerable driver.
- Enforce application control policies such as Windows Defender Application Control or AppLocker to block unauthorized binaries that could trigger the flaw.
- Enable attack surface reduction rules and tamper protection to hinder post-exploitation activity following any successful elevation.
# Verify installed updates addressing CVE-2025-53718
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Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 20
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
