CVE-2026-69474: Windows Overlay Filter Use After Free Flaw

CVE-2026-69474 Overview

CVE-2026-69474 is a use-after-free vulnerability in the Windows Overlay Filter (WOF) driver. An authorized attacker can exploit the flaw over a network to disclose sensitive information from the affected system. The vulnerability is tracked under CWE-126 and requires user interaction along with low-privileged access, which reduces the practical attack surface. Microsoft has published guidance in the Microsoft Security Update Guide CVE-2026-69474.

Critical Impact
Successful exploitation exposes confidential in-memory data from the Windows Overlay Filter component to an authenticated remote attacker.

Affected Products

Microsoft Windows (Windows Overlay Filter component)
Refer to the Microsoft Security Update Guide CVE-2026-69474 for the authoritative list of affected builds
Systems where the Windows Overlay Filter driver (wof.sys) is loaded

Discovery Timeline

2026-09-08 - CVE-2026-69474 published to NVD
2026-09-08 - Last updated in NVD database

Technical Details for CVE-2026-69474

Vulnerability Analysis

The Windows Overlay Filter is a file system filter driver that supports compressed and virtualized file overlays, most commonly used by the Windows Subsystem for Linux and container image layers. A use-after-free condition arises when the driver references an object in memory after it has been released. An authenticated attacker who convinces a user to open a crafted resource can trigger the freed-object access and read residual kernel or process memory contents. Because the confidentiality impact is high but integrity and availability are unaffected, the vulnerability is oriented toward information disclosure rather than code execution.

Root Cause

The root cause is improper object lifetime management inside the Windows Overlay Filter driver. When a filter operation completes, an internal structure is deallocated while a reference to it remains reachable. Subsequent access dereferences freed memory, allowing an attacker to influence what data is read back through carefully timed operations. This class of flaw is categorized under CWE-126: Buffer Over-read as assigned by the CNA.

Attack Vector

Exploitation requires network-reachable access to the target, low-privileged authenticated credentials, and user interaction. The attack complexity is high, reflecting the timing precision required to win the race between free and reuse. No public proof-of-concept exploit is available at the time of publication, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. Refer to the Microsoft advisory for technical details.

Detection Methods for CVE-2026-69474

Indicators of Compromise

Unexpected access patterns to wof.sys or Windows Overlay Filter minifilter callbacks
Anomalous kernel memory read operations originating from low-privileged user sessions
Repeated file operations against virtualized or compressed overlay paths from a single remote principal

Detection Strategies

Monitor Windows event logs and EDR telemetry for abnormal minifilter driver activity tied to the Windows Overlay Filter
Correlate authentication events with unusual file system filter invocations from remote sessions
Alert on process crashes or driver faults referencing wof.sys that could indicate exploit attempts or instability during exploitation

Monitoring Recommendations

Track patch compliance for Microsoft security updates that address CVE-2026-69474 across the fleet
Baseline normal Windows Overlay Filter usage in environments running WSL or container workloads and alert on deviations
Ingest kernel and driver telemetry into a centralized data lake to enable retroactive hunting for exploitation attempts

How to Mitigate CVE-2026-69474

Immediate Actions Required

Apply the Microsoft security update referenced in the Microsoft Security Update Guide CVE-2026-69474 as soon as it is available for your build
Enforce least privilege on remote accounts to reduce the pool of users who satisfy the low-privilege precondition
Restrict inbound network access to Windows hosts that expose file system services to untrusted networks

Patch Information

Microsoft has published guidance for CVE-2026-69474 in the Microsoft Security Update Guide. Administrators should consult that page for the specific KB articles, affected product builds, and fixed versions that correspond to their deployment.

Workarounds

Where the Windows Overlay Filter is not required, review whether dependent features such as WSL or container overlays can be disabled on sensitive hosts
Require user awareness training to reduce the likelihood of the user-interaction step needed for exploitation
Segment networks so that authenticated file system access is limited to trusted management zones

bash

# Configuration example
# Verify installed updates on a Windows host to confirm mitigation coverage
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 20