CVE-2026-69316: Windows Overlay Filter Info Disclosure

CVE-2026-69316 Overview

CVE-2026-69316 is a buffer over-read vulnerability in the Windows Overlay Filter (WOF) driver. An authorized local attacker can exploit the flaw to read memory contents beyond an intended buffer boundary, leading to information disclosure. The issue is categorized under [CWE-126] Buffer Over-read.

Exploitation requires local access and low privileges but has high attack complexity, limiting practical abuse. Successful exploitation impacts confidentiality only; integrity and availability remain unaffected. Microsoft published the advisory through the Microsoft Security Response Center.

Critical Impact
An authenticated local attacker can disclose sensitive kernel or process memory contents by triggering a buffer over-read in the Windows Overlay Filter component.

Affected Products

Microsoft Windows (Windows Overlay Filter component)
Refer to the Microsoft Security Update Guide for the authoritative list of affected builds
Systems using WOF-backed compressed files (CompactOS, WIMBoot, and related features)

Discovery Timeline

2026-09-08 - CVE-2026-69316 published to NVD
2026-09-08 - Last updated in NVD database

Technical Details for CVE-2026-69316

Vulnerability Analysis

The Windows Overlay Filter (wof.sys) is a file system filter driver that provides transparent access to compressed or externally-backed files. It underpins features such as CompactOS, WIMBoot, and single-instance storage for containerized workloads.

CVE-2026-69316 is a buffer over-read [CWE-126]. The driver reads past the end of an allocated buffer during processing of file system metadata or reparse point data. The out-of-bounds read exposes adjacent memory to a caller that should not have access to it.

Because the flaw is in a kernel-mode filter driver, disclosed contents can include kernel pool data, cached file contents, or sensitive process information. That data can support secondary attacks such as ASLR bypass or credential recovery.

Root Cause

The root cause is an insufficient length check when the driver parses length-prefixed or size-tagged structures. A crafted input allows the code to compute a read length that extends beyond the valid bounds of the source buffer, producing an over-read rather than a controlled copy.

Attack Vector

The attack requires local access with valid, low-privileged credentials. The attacker interacts with the Windows Overlay Filter through file system operations that traverse WOF-managed content or reparse points. No user interaction is required. High attack complexity indicates the attacker must satisfy specific timing or state conditions to trigger the over-read reliably.

No public proof-of-concept, exploit code, or in-the-wild exploitation has been reported. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.

Detection Methods for CVE-2026-69316

Indicators of Compromise

Unexpected user-mode processes issuing repeated DeviceIoControl or file operations against WOF-managed paths
Kernel diagnostic events referencing wof.sys or Windows Overlay Filter minifilter callbacks with abnormal frequency
Local, low-privileged accounts staging tools that enumerate or manipulate reparse points and compressed files

Detection Strategies

Baseline normal interaction with WOF-backed files, then alert on statistical outliers from non-administrative users
Correlate file system minifilter telemetry with process ancestry to identify unusual callers of WOF operations
Hunt for local privilege enumeration tooling running alongside repeated access to compressed system files

Monitoring Recommendations

Enable Windows kernel and file system auditing on endpoints that host sensitive workloads
Ingest EDR telemetry covering minifilter driver interactions into a centralized data lake for retrospective analysis
Monitor for post-exploitation behaviors such as credential access or lateral movement following suspicious local access

How to Mitigate CVE-2026-69316

Immediate Actions Required

Apply the Microsoft security update referenced in the Microsoft Security Update Guide as soon as it is released for your Windows build
Inventory endpoints that grant interactive or remote shell access to low-privileged users and prioritize them for patching
Restrict interactive logon rights on servers and workstations that store sensitive data

Patch Information

Microsoft addresses CVE-2026-69316 through its monthly security update channel. Consult the Microsoft Security Update Guide for the specific KB articles, build numbers, and cumulative updates that resolve the buffer over-read in the Windows Overlay Filter driver.

Workarounds

No official vendor workaround is published; patching is the supported remediation path
Reduce exposure by removing unnecessary local accounts and enforcing least-privilege access on affected hosts
Apply application control policies to limit which binaries low-privileged users can execute locally

bash

# Verify installed updates on a Windows host (PowerShell)
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 10

# List minifilter drivers to confirm WOF presence
fltmc filters