CVE-2026-56182: Windows NTFS Privilege Escalation Flaw

CVE-2026-56182 Overview

CVE-2026-56182 is an integer overflow vulnerability in the Windows New Technology File System (NTFS) driver. The flaw allows an authorized local attacker to elevate privileges on an affected Windows host. Microsoft classifies the issue under [CWE-122] Heap-based Buffer Overflow, indicating that the arithmetic wraparound leads to an undersized heap allocation and subsequent memory corruption.

Exploitation requires local access and low privileges, with no user interaction needed. A successful attacker gains high impact on confidentiality, integrity, and availability. Microsoft published the advisory on July 14, 2026, and released a security update through the standard Patch Tuesday channel.

Critical Impact
Successful exploitation grants an authenticated local user SYSTEM-level privileges through NTFS heap corruption, enabling full compromise of the affected Windows host.

Affected Products

Windows operating systems using the NTFS file system driver
Refer to the Microsoft Security Update Guide for the complete list of affected builds
Both client and server Windows editions are typically impacted by NTFS driver vulnerabilities

Discovery Timeline

2026-07-14 - CVE-2026-56182 published to NVD
2026-07-15 - Last updated in NVD database

Technical Details for CVE-2026-56182

Vulnerability Analysis

The vulnerability resides in the NTFS driver code that handles size calculations for file system structures. An integer overflow occurs when arithmetic operations on attacker-influenced values wrap around the maximum representable integer. The wrapped value is then used to allocate a heap buffer that is smaller than the data ultimately written into it.

The subsequent write operation exceeds the allocated buffer boundary, corrupting adjacent kernel heap metadata or object contents. Because NTFS runs in kernel mode, controlled heap corruption in this component can be shaped into an arbitrary write primitive. An attacker who steers the corruption toward a kernel object can pivot to executing code with SYSTEM privileges.

Root Cause

The root cause is missing validation of the result of an integer arithmetic operation used to size a heap allocation, classified as [CWE-122] Heap-based Buffer Overflow. When user-controlled inputs cause the size calculation to wrap, NTFS proceeds to allocate an undersized buffer and copies attacker-supplied data into it without a bounds check against the original, unwrapped length.

Attack Vector

The attack vector is local and requires the attacker to already hold a valid account on the target system. An attacker triggers the vulnerable code path by crafting a malicious file system operation, such as a specially formed request against a mounted NTFS volume or a specifically constructed on-disk NTFS structure. No user interaction is required, and the scope remains unchanged, meaning the impact is contained to the vulnerable Windows security authority.

No public proof-of-concept exploit was available at the time of publication. Microsoft has not reported active exploitation, and the CVE is not listed in the CISA Known Exploited Vulnerabilities catalog.

Detection Methods for CVE-2026-56182

Indicators of Compromise

Unexpected System or ntoskrnl.exe crashes with bug check codes referencing NTFS (for example, NTFS_FILE_SYSTEM 0x24) shortly after non-administrative user activity
New processes spawned as NT AUTHORITY\SYSTEM from parent processes owned by standard users
Anomalous file system operations targeting raw NTFS structures from non-administrative accounts

Detection Strategies

Monitor Windows Error Reporting and kernel crash telemetry for NTFS-related bug checks correlated with local user sessions
Alert on privilege escalation patterns where a low-privileged process token is followed by SYSTEM-owned child processes
Baseline normal NTFS driver interactions and flag deviations such as unusual IRP_MJ_FILE_SYSTEM_CONTROL request volumes from user-mode processes

Monitoring Recommendations

Enable kernel-mode event tracing (ETW) for the NTFS provider and forward events to a centralized log platform
Track Sysmon Event IDs 1 (process create) and 10 (process access) for evidence of token manipulation following local user activity
Retain memory dumps generated by NTFS bug checks for offline analysis rather than discarding them automatically

How to Mitigate CVE-2026-56182

Immediate Actions Required

Apply the July 2026 Microsoft security update referenced in the Microsoft Security Update Guide to all affected Windows systems
Prioritize patching multi-user systems, terminal servers, and virtual desktop infrastructure where local accounts are most numerous
Audit local account privileges and remove standing local logon rights that are not operationally required

Patch Information

Microsoft released a security patch addressing CVE-2026-56182 through Windows Update. Administrators should consult the Microsoft Security Update Guide entry for CVE-2026-56182 for the specific Knowledge Base article numbers and build revisions applicable to each supported Windows version. Deploy the update through Windows Server Update Services (WSUS), Microsoft Intune, or the equivalent enterprise patch management tool.

Workarounds

No official workaround has been published by Microsoft; patching is the supported remediation
Restrict interactive and remote logon rights on sensitive hosts to reduce the pool of accounts capable of local exploitation
Enforce application allowlisting to limit the ability of untrusted binaries to interact with NTFS in unusual ways

bash

# Verify installed update on a Windows host (PowerShell)
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 10

# Query the current NTFS driver version
Get-Item C:\Windows\System32\drivers\ntfs.sys | Select-Object VersionInfo