CVE-2026-50362: Windows 10 1607 Buffer Overflow Vulnerability

CVE-2026-50362 Overview

CVE-2026-50362 is a heap-based buffer overflow [CWE-122] in the Windows Resilient File System (ReFS) driver. The flaw allows a local, unauthenticated attacker to execute arbitrary code after a user interacts with attacker-supplied content. Microsoft has confirmed the issue affects supported Windows client and server releases, including Windows 10, Windows 11, and Windows Server 2016 through 2025.

Exploitation requires local access and user interaction, but successful attacks yield high impact to confidentiality, integrity, and availability. The vulnerability is tracked in the Microsoft CVE-2026-50362 Update Guide.

Critical Impact
Attackers can achieve local code execution on unpatched Windows systems by tricking a user into mounting or opening a crafted ReFS volume, potentially leading to full system compromise.

Affected Products

Microsoft Windows 10 (1607, 1809, 21H2, 22H2) across x86, x64, and ARM64
Microsoft Windows 11 (24H2, 25H2, 26H1) across x64 and ARM64
Microsoft Windows Server 2016, 2019, 2022, and 2025

Discovery Timeline

2026-07-14 - CVE-2026-50362 published to NVD
2026-07-20 - Last updated in NVD database

Technical Details for CVE-2026-50362

Vulnerability Analysis

The vulnerability resides in the Windows Resilient File System (ReFS) driver, which handles metadata parsing for ReFS-formatted volumes. A heap-based buffer overflow occurs when ReFS processes malformed on-disk structures. The driver writes beyond the bounds of a heap-allocated buffer, corrupting adjacent kernel or user-mode memory.

Because ReFS runs with elevated privilege as a file system driver, memory corruption in this code path can be steered toward arbitrary code execution. The Common Weakness Enumeration classification is [CWE-122] Heap-based Buffer Overflow.

Root Cause

The root cause is improper validation of length or offset fields inside ReFS metadata structures before they are used to size or index a heap allocation. When an attacker-controlled value exceeds the allocated buffer, the driver copies data past the buffer boundary. This overwrites adjacent heap chunks and can corrupt object headers or function pointers used later by the kernel.

Attack Vector

Exploitation requires local access and user interaction. A typical attack scenario involves an attacker delivering a crafted ReFS volume image, such as a VHD or VHDX file, that the target user mounts or opens. When Windows parses the malicious volume, the vulnerable ReFS code path triggers the overflow.

No authentication is required prior to exploitation. Once code execution is achieved, the attacker can install programs, view or alter data, or create accounts with elevated rights. Public proof-of-concept code is not currently available, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.

Refer to the Microsoft CVE-2026-50362 Update Guide for vendor-specific technical detail.

Detection Methods for CVE-2026-50362

Indicators of Compromise

Unexpected mounting of ReFS-formatted virtual disks (.vhd, .vhdx, .iso) delivered via email, chat, or removable media
Crashes or bug checks originating from refs.sys or refsv1.sys on affected Windows versions
Creation of new privileged local accounts or scheduled tasks immediately following a volume mount event

Detection Strategies

Monitor Windows Event Log for kernel-mode crashes referencing the ReFS driver, which may indicate failed exploitation attempts
Alert on process chains where user applications mount virtual disk images followed by suspicious child process creation from System or svchost.exe
Inspect endpoint telemetry for unusual disk image downloads followed by shell invocations or LOLBIN activity

Monitoring Recommendations

Enable auditing of virtual disk mount and dismount operations, including Mount-VHD PowerShell cmdlet usage
Correlate file system driver crash dumps with recent user file activity to identify suspicious volume images
Track privilege escalation events and new service installations that occur within a short window of ReFS volume access

How to Mitigate CVE-2026-50362

Immediate Actions Required

Apply the Microsoft security update referenced in the Microsoft CVE-2026-50362 Update Guide to all affected Windows client and server systems
Prioritize patching on systems that regularly mount user-supplied virtual disk images, including administrator workstations and Hyper-V hosts
Restrict end users from mounting untrusted .vhd, .vhdx, or .iso files received from external sources

Patch Information

Microsoft has published fixes through its Update Guide for all listed Windows 10, Windows 11, and Windows Server releases. Administrators should deploy the corresponding cumulative update for each build. Consult the Microsoft CVE-2026-50362 Update Guide for KB article numbers matched to each affected version.

Workarounds

Block or quarantine inbound virtual disk file types at the email gateway and web proxy
Use Group Policy or AppLocker to restrict execution of virtual disk mounting utilities to authorized administrators
Where ReFS is not required, avoid formatting user-facing volumes with ReFS and disable automatic mounting of removable media

bash

# Configuration example: disable automatic mounting of new volumes via diskpart
diskpart
automount disable
automount scrub
exit