CVE-2026-68875: Windows NTFS Buffer Overflow Vulnerability

CVE-2026-68875 Overview

CVE-2026-68875 is a buffer over-read vulnerability in the Windows NTFS file system driver. An authorized local attacker can exploit the flaw to execute code on the target host. The weakness is classified under [CWE-126] (Buffer Over-read), where the driver reads memory past the end of an intended buffer during NTFS operations. Successful exploitation compromises confidentiality, integrity, and availability on the affected system. Microsoft published the advisory in its Security Update Guide.

Critical Impact
A low-privileged local user can trigger the NTFS over-read to gain code execution and escalate control over the host.

Affected Products

Microsoft Windows (NTFS file system driver)
Refer to the Microsoft Security Update Guide CVE-2026-68875 for the full list of affected Windows builds

Discovery Timeline

2026-09-08 - CVE-2026-68875 published to the National Vulnerability Database
2026-09-09 - Last updated in NVD database

Technical Details for CVE-2026-68875

Vulnerability Analysis

The vulnerability resides in the New Technology File System (NTFS) driver shipped with Windows. NTFS parses on-disk metadata structures such as Master File Table (MFT) records, attributes, and index entries. A buffer over-read occurs when the driver reads bytes beyond an allocated buffer while processing a crafted NTFS structure. Reading past the buffer boundary can leak adjacent kernel memory and, when combined with attacker-controlled state, redirect execution flow. Microsoft categorizes the outcome as local code execution rather than pure information disclosure. Attack complexity is low and user interaction is not required, which shortens the exploitation path once an attacker has an authenticated foothold.

Root Cause

The root cause is missing or insufficient bounds validation on NTFS metadata fields before the driver reads from a buffer. [CWE-126] describes this class of defect: the read length or offset derives from untrusted input without ensuring it stays within the buffer. Malformed record sizes, attribute lengths, or index header fields in a crafted volume can drive the over-read.

Attack Vector

Exploitation requires local access with low privileges. A typical path is mounting or accessing a crafted NTFS volume, such as a VHD, VHDX, ISO, or removable image, that contains malformed metadata. When the NTFS driver parses the poisoned structure, it reads past buffer boundaries in kernel context. An attacker who controls adjacent memory can convert the over-read into arbitrary code execution at kernel privilege. No verified public proof-of-concept is listed in the enriched data.

See the Microsoft Security Update Guide CVE-2026-68875 for vendor technical detail.

Detection Methods for CVE-2026-68875

Indicators of Compromise

Unexpected mounting of VHD, VHDX, or ISO images by non-administrative users
Kernel-mode crashes referencing ntfs.sys in Windows Error Reporting or minidumps
Creation of new services, scheduled tasks, or drivers immediately after a volume-mount event
Event ID 55 (chkdsk) or NTFS-related System log entries preceding privilege changes

Detection Strategies

Alert on Microsoft-Windows-VHDMP events and Mount-DiskImage PowerShell invocations from standard user contexts
Correlate NTFS driver crashes with subsequent process creation events using SYSTEM tokens
Hunt for unsigned or unusual images written to user-writable paths and then attached as disks

Monitoring Recommendations

Enable kernel crash dump collection and forward ntfs.sys faults to a central analytics pipeline
Ingest Windows Security, System, and Sysmon events into a SIEM to correlate mount, load, and privilege-escalation activity
Track patch state of Windows endpoints against the Microsoft advisory for CVE-2026-68875

How to Mitigate CVE-2026-68875

Immediate Actions Required

Apply the Microsoft security update referenced in the Microsoft Security Update Guide CVE-2026-68875 as soon as testing allows
Prioritize patching of multi-user hosts, jump servers, and VDI images where local attackers are most likely
Audit which local accounts can mount disk images and remove the privilege where it is not required

Patch Information

Microsoft addresses CVE-2026-68875 through the update listed in the Security Update Guide. Deploy the cumulative update matching each Windows build in the environment. Validate installation by checking the OS build number against the Microsoft KB entry for the release.

Workarounds

Restrict attachment of untrusted VHD, VHDX, and ISO files through Group Policy and AppLocker
Disable auto-mount of removable media and block USB mass-storage where operationally acceptable
Enforce least privilege so standard users cannot install drivers or mount arbitrary volumes

bash

# Disable automatic mounting of new volumes (run as administrator)
diskpart
automount disable
automount scrub
exit