CVE-2026-62797: Windows 10 1607 Privilege Escalation Flaw

CVE-2026-62797 Overview

CVE-2026-62797 is a heap-based buffer overflow vulnerability in the Windows NTFS file system driver. An authenticated local attacker can exploit this flaw to elevate privileges on affected Windows client and server systems. The vulnerability is tracked under CWE-122: Heap-based Buffer Overflow and affects a broad range of supported Windows releases, including Windows 10, Windows 11, and Windows Server editions from 2012 through 2025.

Microsoft published the advisory through the Microsoft Security Response Center. Successful exploitation yields high confidentiality, integrity, and availability impact on the compromised host.

Critical Impact
A local, low-privileged attacker can trigger a heap overflow in the NTFS driver to gain elevated privileges, potentially reaching SYSTEM-level access on Windows endpoints and servers.

Affected Products

Microsoft Windows 10 (1607, 1809, 21H2, 22H2) across x86, x64, and ARM64 architectures
Microsoft Windows 11 (23H2, 24H2, 25H2, 26H1) across x64 and ARM64 architectures
Microsoft Windows Server 2012, 2012 R2, 2016, 2019, 2022, and 2025

Discovery Timeline

2026-08-11 - CVE-2026-62797 published to the National Vulnerability Database
2026-08-13 - Last updated in NVD database

Technical Details for CVE-2026-62797

Vulnerability Analysis

The vulnerability resides in the NTFS driver, which handles file system operations for the New Technology File System on Windows. A heap-based buffer overflow occurs when the driver writes data beyond the bounds of an allocated buffer on the kernel heap. Because NTFS runs in kernel mode, corruption of adjacent heap structures can be leveraged to manipulate kernel objects and escalate privileges.

The attack requires local access and low privileges, but no user interaction. This aligns with the profile of a privilege escalation primitive typically chained with an initial access technique such as phishing, malicious document execution, or a compromised low-privilege service account. The EPSS score at publication was approximately 0.34%, indicating a low near-term probability of mass exploitation, though local EoP bugs frequently see targeted use in post-exploitation activity.

Root Cause

The root cause is improper validation of size or length parameters before writing to a heap-allocated buffer inside the NTFS driver. When a specially crafted file system structure or ioctl request is processed, the driver copies attacker-controlled data past the buffer boundary, corrupting adjacent kernel heap memory. Microsoft has not released source-level details of the specific code path.

Attack Vector

Exploitation requires the attacker to already hold an authenticated session on the target with at least standard user rights. The attacker crafts a malicious NTFS on-disk structure, mounted volume, or driver request that triggers the vulnerable code path in ntfs.sys. Successful heap corruption enables kernel object manipulation, leading to token replacement or arbitrary kernel read/write and ultimately SYSTEM privileges.

No public proof-of-concept exploit or CISA KEV listing exists at the time of publication. Refer to the Microsoft CVE-2026-62797 Advisory for authoritative technical guidance.

Detection Methods for CVE-2026-62797

Indicators of Compromise

Unexpected creation of processes running as NT AUTHORITY\SYSTEM from parent processes owned by standard users
Kernel bugchecks or system crashes referencing ntfs.sys on hosts where a low-privileged user was recently active
Mounting or attachment of unusual VHD, VHDX, or ISO images containing crafted NTFS volumes by non-administrative users
Loading of unsigned or unusual drivers immediately following NTFS-related kernel events

Detection Strategies

Monitor Windows Event Log for kernel-mode faults, BugCheck events (Event ID 1001), and NTFS-specific errors correlated with local logon sessions
Alert on token manipulation patterns where a process's integrity level or user SID changes mid-execution
Baseline and flag anomalous use of IOCTL_DISK_* and NTFS control codes issued by non-administrative processes
Deploy behavioral endpoint detection rules that identify local privilege escalation chains, including sudden SYSTEM-level child processes spawned from user-context binaries

Monitoring Recommendations

Enable Windows Defender Application Control or WDAC audit mode to log driver and image loads across affected fleets
Forward Sysmon Event IDs 1 (process creation), 6 (driver load), and 10 (process access) to a centralized SIEM for correlation
Review Microsoft-Windows-Ntfs/Operational logs for repeated volume mount failures or structural errors

How to Mitigate CVE-2026-62797

Immediate Actions Required

Apply the Microsoft security update referenced in the MSRC advisory to all affected Windows client and server systems
Prioritize patching on multi-user systems, terminal servers, and jump hosts where local low-privilege access is common
Audit local user accounts and remove unnecessary interactive logon rights on servers
Restrict the ability of standard users to mount arbitrary VHD, VHDX, and ISO images

Patch Information

Microsoft has released cumulative security updates addressing CVE-2026-62797 for all supported Windows 10, Windows 11, and Windows Server versions listed in the advisory. Administrators should consult the Microsoft CVE-2026-62797 Advisory for the specific KB article numbers corresponding to each affected build and deploy them through Windows Update, WSUS, Intune, or the Microsoft Update Catalog.

Workarounds

No official vendor workaround has been published; patching is the required remediation path
Reduce risk by enforcing least-privilege access and disabling shell access for service accounts
Use Group Policy or Intune to block standard users from mounting removable and virtual disk media
Apply application control policies to prevent unauthorized binaries from executing local privilege escalation tooling

bash

# Verify installed updates on a Windows host (PowerShell)
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 20

# Restrict virtual disk mounting for non-administrators via Group Policy path:
# Computer Configuration > Administrative Templates > System > Removable Storage Access
# Set "All Removable Storage classes: Deny all access" as appropriate to the environment