CVE-2026-50341: Windows NTFS Information Disclosure Flaw

CVE-2026-50341 Overview

CVE-2026-50341 is a buffer over-read vulnerability in the Windows New Technology File System (NTFS) driver. An authenticated local attacker can trigger the flaw to read memory beyond an allocated buffer, resulting in information disclosure. The weakness is classified under [CWE-126] Buffer Over-read and affects the confidentiality of data processed by the NTFS component. Microsoft published the advisory on July 14, 2026, and updated it on July 16, 2026. No public exploit code, CISA Known Exploited Vulnerabilities (KEV) listing, or proof-of-concept has been reported at the time of publication.

Critical Impact
Local, authenticated attackers can read out-of-bounds NTFS memory to disclose sensitive kernel or file system data on affected Windows hosts.

Affected Products

Microsoft Windows (NTFS driver component)
Refer to the Microsoft Security Update Guide for the authoritative list of affected builds
Specific SKUs and version numbers not enumerated in NVD data at time of publication

Discovery Timeline

2026-07-14 - CVE-2026-50341 published to NVD
2026-07-16 - Last updated in NVD database

Technical Details for CVE-2026-50341

Vulnerability Analysis

The vulnerability resides in the NTFS file system driver, which parses on-disk structures and services file system requests from user-mode callers. A buffer over-read occurs when the driver reads past the end of an allocated memory region during processing of NTFS metadata or user-supplied input. The out-of-bounds read exposes adjacent memory contents to the caller. Attackers who can invoke the vulnerable code path obtain data that should not be accessible under normal access controls.

The impact is limited to confidentiality. Integrity and availability of the target system are not affected according to the published metrics. Exploitation requires local access and low-privileged authentication, and does not require user interaction.

EPSS data as of 2026-07-20 lists a low probability of near-term exploitation, but information disclosure primitives in kernel-mode drivers are frequently chained with other flaws to bypass mitigations such as Kernel Address Space Layout Randomization (KASLR).

Root Cause

The root cause is a boundary check failure in NTFS parsing logic, categorized as [CWE-126] Buffer Over-read. The driver reads from a buffer using a length or index derived from untrusted input without validating that the read stays within the allocated region. Microsoft has not publicly disclosed the specific function or structure affected.

Attack Vector

Exploitation requires local access to the target system and a valid low-privileged account. The attacker interacts with the NTFS driver through standard file system APIs or by mounting a crafted volume. The driver processes the malformed input and returns memory contents from beyond the intended buffer boundary. User interaction is not required.

No verified proof-of-concept code is publicly available. See the Microsoft Security Update Guide for vendor technical details.

Detection Methods for CVE-2026-50341

Indicators of Compromise

No public indicators of compromise have been published for CVE-2026-50341
Unexpected mounting of user-supplied virtual hard disk (VHD/VHDX) or ISO images by low-privileged accounts
Anomalous NTFS driver crashes or bug checks recorded in Windows Event Log or memory dumps

Detection Strategies

Monitor for unsigned or unusual processes issuing raw file system control (FSCTL) operations against NTFS volumes
Correlate mount events for removable or virtual disk images with subsequent access to sensitive process memory or system files
Baseline normal NTFS driver behavior and alert on repeated failed reads or unexpected kernel-mode exceptions in ntfs.sys

Monitoring Recommendations

Enable Windows Defender Application Control or AppLocker to restrict which low-privileged users can execute disk-mount utilities
Forward Sysmon and Windows Security event logs to a centralized SIEM for correlation with authentication activity
Track patch compliance for all Windows hosts and flag systems missing the July 2026 security update

How to Mitigate CVE-2026-50341

Immediate Actions Required

Apply the Microsoft security update referenced in the MSRC advisory for CVE-2026-50341 as soon as testing permits
Inventory Windows endpoints and servers to identify hosts running vulnerable NTFS driver versions
Restrict interactive and remote logon rights on multi-user systems to reduce the population of accounts that can trigger local attacks

Patch Information

Microsoft has released a security update addressing CVE-2026-50341. Administrators should consult the Microsoft Security Update Guide for the specific Knowledge Base article, affected product builds, and update packages applicable to their environment. Deploy the update through Windows Update, Windows Server Update Services (WSUS), Microsoft Configuration Manager, or a comparable patch management platform.

Workarounds

No vendor-supplied workaround has been published; patching is the primary remediation
Disable the ability for non-administrative users to mount arbitrary VHD, VHDX, or ISO files where operationally feasible
Enforce least-privilege access on file shares and local accounts to limit the value of any disclosed memory contents

bash

# Verify the installed Windows build and confirm the July 2026 update is present
systeminfo | findstr /B /C:"OS Name" /C:"OS Version"
wmic qfe list brief /format:table