CVE-2026-58640: Windows 10 1607 Buffer Overflow Flaw

CVE-2026-58640 Overview

CVE-2026-58640 is a heap-based buffer overflow vulnerability in the Windows New Technology File System (NTFS) driver. An authenticated local attacker can trigger the overflow to execute arbitrary code on affected systems. The flaw is classified under [CWE-122: Heap-based Buffer Overflow] and impacts a broad range of Microsoft Windows client and server editions, from Windows 10 1607 through Windows 11 26H1 and Windows Server 2012 through Windows Server 2025.

Microsoft published the advisory on July 14, 2026 through the Microsoft Security Response Center (MSRC).

Critical Impact
Successful exploitation grants an authorized local attacker code execution with elevated privileges, resulting in full compromise of confidentiality, integrity, and availability on the affected host.

Affected Products

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

Discovery Timeline

2026-07-14 - CVE-2026-58640 published to NVD
2026-07-17 - Last updated in NVD database

Technical Details for CVE-2026-58640

Vulnerability Analysis

The vulnerability resides in the NTFS file system driver, a core kernel-mode component responsible for parsing and managing on-disk NTFS structures. A heap-based buffer overflow occurs when the driver writes data beyond the bounds of a dynamically allocated buffer on the kernel pool. Because NTFS operates in kernel context, memory corruption in this component translates directly into elevated code execution.

Exploitation requires local access and low-privilege authenticated credentials. No user interaction is needed, and the attack complexity is low. An attacker with a standard user account can leverage the flaw to elevate to SYSTEM.

Root Cause

The root cause is improper validation of size or length parameters when NTFS processes attacker-influenced metadata or file system structures. The driver allocates a heap buffer based on one value, then copies data using a different or attacker-controlled length, resulting in an out-of-bounds write on the kernel pool. This maps to [CWE-122].

Attack Vector

The attack vector is local. A typical exploitation path involves an attacker crafting a malicious NTFS structure — for example, a specially formed virtual hard disk (VHD/VHDX) image, a mounted volume, or a specific sequence of file operations — that the NTFS driver parses. When the vulnerable code path executes, the overflow corrupts adjacent pool memory. Attackers commonly chain such primitives with pool grooming techniques to overwrite kernel objects and gain arbitrary code execution in ring 0.

No public proof-of-concept or in-the-wild exploitation has been reported at the time of publication, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.

See the Microsoft Security Update CVE-2026-58640 advisory for authoritative technical details.

Detection Methods for CVE-2026-58640

Indicators of Compromise

Unexpected mounting of VHD, VHDX, or ISO images by standard user accounts, especially from writable user-controlled paths.
Kernel bugchecks or NTFS.sys crashes (STOP 0x00000024 NTFS_FILE_SYSTEM) followed by process privilege changes.
Standard user processes spawning children as NT AUTHORITY\SYSTEM shortly after file system activity.
Creation or modification of suspicious .vhd, .vhdx, or raw disk image files in temporary or user-writable directories.

Detection Strategies

Hunt for local privilege escalation patterns: a non-elevated process performing file system operations followed by a SYSTEM-integrity child process on the same host.
Alert on use of diskpart, PowerShell Mount-DiskImage, or Mount-VHD cmdlets executed by non-administrative accounts.
Monitor Windows Event Log for repeated NTFS (Event IDs 55, 130, 137) and Volume errors that may indicate exploitation attempts.
Correlate kernel crash dumps referencing Ntfs! symbols with subsequent anomalous authentication or process lineage events.

Monitoring Recommendations

Enable and forward Sysmon Event ID 1 (process creation) and Event ID 11 (file create) with rules covering disk image files and NTFS utilities.
Ingest kernel WER (Windows Error Reporting) telemetry and driver crash reports into a centralized data lake for correlation.
Track patch compliance across all listed Windows client and server versions and flag hosts missing the July 2026 cumulative update.
Baseline normal VHD/VHDX usage per host and alert on deviations, particularly on servers where disk image mounting is atypical.

How to Mitigate CVE-2026-58640

Immediate Actions Required

Apply the July 2026 Microsoft security update for CVE-2026-58640 to all affected Windows 10, Windows 11, and Windows Server systems.
Prioritize patching of multi-user systems, terminal servers, VDI hosts, and shared workstations where low-privilege users execute code.
Restrict the ability of standard users to mount disk images or attach VHD/VHDX files via Group Policy or AppLocker.
Audit local accounts and remove unnecessary interactive logon rights on servers.

Patch Information

Microsoft has released security updates through the MSRC. Refer to the Microsoft Security Update CVE-2026-58640 advisory for the specific KB article and build numbers corresponding to each affected Windows release. Deploy the update through Windows Update, WSUS, Microsoft Configuration Manager, or Intune according to your patch management process.

Workarounds

No official workaround is documented by Microsoft; patching is the required remediation.
As a compensating control, block standard users from mounting arbitrary disk images by removing the SeManageVolumePrivilege and restricting Explorer shell mounting via Group Policy.
Enforce the principle of least privilege so that untrusted users cannot obtain interactive or remote desktop access on unpatched hosts.
Enable Windows Defender Exploit Guard and kernel-mode integrity protections (HVCI, Kernel DMA Protection) to raise the cost of pool corruption exploits.

bash

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

# Restrict non-admin VHD mounting via Group Policy registry key
reg add "HKLM\SOFTWARE\Policies\Microsoft\Windows\RemovableStorageDevices" /v Deny_All /t REG_DWORD /d 1 /f