CVE-2025-53147 Overview
CVE-2025-53147 is a use-after-free vulnerability [CWE-416] in the Windows Ancillary Function Driver for WinSock (afd.sys). The flaw allows an authorized local attacker to elevate privileges on affected Windows systems. Microsoft published the advisory on August 12, 2025, and the issue affects a broad range of Windows client and server editions, including Windows 10, Windows 11, and Windows Server versions from 2008 through 2025.
Successful exploitation grants SYSTEM-level privileges, giving attackers full control over the target host. The Ancillary Function Driver is a kernel-mode component that supports Windows Sockets, making it a recurring target for local privilege escalation research.
Critical Impact
Local attackers with low-privileged access can escalate to SYSTEM privileges through a use-after-free condition in a core Windows kernel driver.
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-2025-53147 published to NVD
- 2025-08-12 - Microsoft releases security update via the Microsoft Security Update Guide for CVE-2025-53147
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-53147
Vulnerability Analysis
The vulnerability resides in the Windows Ancillary Function Driver for WinSock (afd.sys), a kernel-mode driver that provides support for the Windows Sockets API. A use-after-free condition [CWE-416] occurs when the driver frees a kernel object but retains a reference that is later dereferenced during socket-related operations.
An authorized local attacker can trigger the flawed code path by issuing crafted IOCTL requests or socket operations against afd.sys. Once the freed object is reallocated with attacker-controlled data, subsequent dereference operations execute code in kernel context. This yields elevation from a standard user account to SYSTEM.
Exploitation requires local access and a valid low-privileged account. The attack complexity is high because reliable exploitation depends on winning a timing window between the free and reuse of the affected kernel object.
Root Cause
The root cause is improper object lifetime management within afd.sys. The driver releases a kernel allocation while another code path continues to hold and later access the stale pointer. Windows kernel pool allocations can be reclaimed by attacker-controlled data through well-known heap grooming techniques, converting the dangling reference into a controlled write or execution primitive.
Attack Vector
The attack vector is local. An attacker executes code on the target with standard user privileges, then interacts with afd.sys through documented and undocumented socket interfaces to trigger the vulnerable state. No user interaction is required beyond the attacker's own process activity. See the Microsoft Security Update Guide for CVE-2025-53147 for vendor-provided details.
No public proof-of-concept exploit is currently available, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.
Detection Methods for CVE-2025-53147
Indicators of Compromise
- Unexpected SYSTEM-level processes spawned from low-privileged user sessions
- Kernel bugchecks (BSOD) referencing afd.sys on unpatched hosts, which may indicate failed exploitation attempts
- Newly created services, scheduled tasks, or persistence artifacts following interactive logons by non-administrative users
Detection Strategies
- Monitor for anomalous process token elevation where child processes of standard user sessions run as NT AUTHORITY\SYSTEM
- Correlate driver crash telemetry (WER, MiniDump) referencing afd.sys with subsequent privileged process creation on the same host
- Baseline normal socket-driver interactions and alert on atypical high-frequency IOCTL patterns from user-mode processes targeting \Device\Afd
Monitoring Recommendations
- Enable Windows Kernel-Mode Driver Framework auditing and forward events to a centralized SIEM for correlation
- Track patch compliance across all affected Windows client and server editions using vulnerability management tooling
- Review Sysmon Event ID 1 (process creation) and Event ID 10 (process access) for suspicious escalations from standard user contexts
How to Mitigate CVE-2025-53147
Immediate Actions Required
- Apply the Microsoft security update referenced in the Microsoft Security Update Guide for CVE-2025-53147 to all affected Windows systems
- Prioritize patching multi-user systems, terminal servers, and hosts where untrusted users can execute code
- Enforce the principle of least privilege and remove unnecessary local logon rights for standard accounts
Patch Information
Microsoft released fixes as part of the August 2025 security update cycle. Administrators should consult the Microsoft Security Update Guide for CVE-2025-53147 for the specific KB article and build numbers corresponding to each supported Windows version. Apply cumulative updates through Windows Update, WSUS, Microsoft Update Catalog, or an enterprise patching solution.
Workarounds
- No official workarounds have been published by Microsoft; patching is the required remediation
- Restrict local and interactive logon rights on servers to reduce the population of accounts able to trigger the flaw
- Deploy application control policies (AppLocker, Windows Defender Application Control) to limit execution of unauthorized binaries by standard users
# Verify installed updates on Windows (PowerShell)
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 20
# Confirm afd.sys file version after patching
Get-Item C:\Windows\System32\drivers\afd.sys | Select-Object VersionInfo
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
