CVE-2026-50448: Windows NTFS Buffer Overflow Vulnerability

CVE-2026-50448 Overview

CVE-2026-50448 is a heap-based buffer overflow vulnerability in the Windows New Technology File System (NTFS). The flaw allows an unauthorized local attacker to execute arbitrary code on an affected system. Exploitation requires user interaction, typically achieved by convincing a user to mount or interact with a crafted NTFS volume or file.

The issue is tracked under CWE-122 (Heap-based Buffer Overflow) and carries a CVSS 3.1 base score of 7.8. Microsoft published the advisory in the Microsoft Security Update Guide.

Critical Impact
Successful exploitation grants attackers the ability to execute code locally with the confidentiality, integrity, and availability of the host all fully impacted.

Affected Products

Microsoft Windows (NTFS component)
Refer to the Microsoft Security Update Guide for the complete list of affected builds
Specific product and build enumeration not published in NVD at the time of writing

Discovery Timeline

2026-07-14 - CVE-2026-50448 published to the National Vulnerability Database
2026-07-15 - Last updated in NVD database

Technical Details for CVE-2026-50448

Vulnerability Analysis

The vulnerability resides in the NTFS driver, which parses on-disk file system structures when a volume is mounted or accessed. A heap-based buffer overflow occurs when the driver processes malformed metadata and writes past the bounds of a heap-allocated buffer. Because NTFS parsing happens in kernel context, memory corruption in this code path can lead to arbitrary code execution with elevated privileges.

Exploitation is local and requires user interaction. A common scenario involves an attacker delivering a crafted virtual hard disk (VHD) or removable media containing a malicious NTFS volume. When the user mounts or opens the volume, the driver processes the malformed structure and triggers the overflow.

The EPSS score at publication is approximately 0.343% (26th percentile), indicating a low current probability of observed exploitation. There is no public proof-of-concept or CISA Known Exploited Vulnerabilities listing at this time.

Root Cause

The root cause is insufficient validation of size or length fields within NTFS on-disk structures. The driver allocates a heap buffer based on one value and then copies data using a separate, attacker-controlled length, resulting in an out-of-bounds heap write consistent with CWE-122.

Attack Vector

The attack vector is local (AV:L) with low complexity, no privileges required, and user interaction required. An attacker crafts a malicious NTFS image and delivers it via removable media, a network share, a phishing attachment containing a VHD or ISO, or a mountable disk image. When the victim mounts or browses the volume, the vulnerable code path executes and corrupts kernel heap memory.

No verified public exploit code is available. Refer to the Microsoft Security Update Guide for vendor technical details.

Detection Methods for CVE-2026-50448

Indicators of Compromise

Unexpected mounting of VHD, VHDX, or ISO files from user download directories or email attachments
System crashes or bugchecks (BSOD) referencing ntfs.sys shortly after mounting removable or virtual media
New kernel-mode processes or drivers loaded immediately following NTFS volume interaction
Anomalous child processes spawned from explorer.exe or mountvol.exe after image mount events

Detection Strategies

Monitor Windows Event Log IDs 98 and 55 from source Ntfs for corruption or structure integrity errors
Alert on Microsoft-Windows-VHDMP events indicating mount operations of files originating from untrusted paths
Correlate crash dumps citing ntfs.sys faulting modules with recent file mount or file access activity
Apply behavioral rules for kernel memory corruption patterns followed by privilege escalation attempts

Monitoring Recommendations

Enable PowerShell and Sysmon logging of FileCreate events for .vhd, .vhdx, .iso, and .img extensions in user-writable directories
Track process creation events where mountvol, diskpart, or Explorer shell operations mount images from download or temp folders
Aggregate kernel crash telemetry centrally and flag repeated ntfs.sys faults on the same host

How to Mitigate CVE-2026-50448

Immediate Actions Required

Apply the Microsoft security update referenced in the Microsoft Security Update Guide as soon as it is available for your Windows build
Prioritize patching endpoints that routinely mount external media, VHDs, or ISOs, including workstations used by IT and developers
Restrict end-user permissions to mount virtual disk files where operationally feasible

Patch Information

Microsoft addresses CVE-2026-50448 through its monthly security update channel. Administrators should consult the Microsoft Security Update Guide to identify the specific KB article and update package that applies to each affected Windows version, then deploy through Windows Update, WSUS, Microsoft Intune, or Configuration Manager.

Workarounds

Block delivery of .vhd, .vhdx, .iso, and .img files at the email gateway and web proxy where business use cases permit
Disable automatic mounting of removable media and virtual disks through Group Policy on high-risk endpoints
Enforce Attack Surface Reduction (ASR) rules that block execution of content from removable media
Use Windows Defender Application Control or AppLocker to prevent execution of unsigned binaries staged from mounted images

bash

# Group Policy example: block automatic mounting of new volumes
# Registry path applied via GPO or reg.exe
reg add "HKLM\SYSTEM\CurrentControlSet\Services\mountmgr" /v NoAutoMount /t REG_DWORD /d 1 /f

# Restrict Explorer shell from opening ISO/VHD via default handler
reg add "HKLM\SOFTWARE\Policies\Microsoft\Windows\Explorer" /v NoAutoplayfornonVolume /t REG_DWORD /d 1 /f