CVE-2025-49678 Overview
CVE-2025-49678 is a local privilege escalation vulnerability in the Windows NTFS file system driver. The flaw stems from a null pointer dereference triggered under specific race conditions, classified as [CWE-362]. An authorized local attacker who wins the race can elevate privileges on the affected host.
Microsoft assigned this issue a CVSS 3.1 base score of 7.0. The vulnerability affects a broad range of Windows client and server releases, from Windows 10 1507 through Windows 11 24H2 and from Windows Server 2008 through Windows Server 2025.
Critical Impact
A local, authenticated attacker who successfully exploits the race condition in NTFS gains higher privileges on the host, breaking the boundary between standard users and privileged system components.
Affected Products
- Microsoft Windows 10 (1507, 1607, 1809, 21H2, 22H2)
- Microsoft Windows 11 (22H2, 23H2, 24H2)
- Microsoft Windows Server 2008, 2012, 2016, 2019, 2022, 2022 23H2, and 2025
Discovery Timeline
- 2025-07-08 - CVE-2025-49678 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-49678
Vulnerability Analysis
The vulnerability lives in the NTFS driver (ntfs.sys), which handles file system operations for the primary Windows storage stack. NTFS runs in kernel mode, so any dereference of an invalid pointer executes at ring 0. A concurrency defect allows a pointer to be consumed before it is initialized or after it has been cleared, producing a null pointer dereference in kernel context.
The issue is mapped to [CWE-362], a concurrent execution flaw involving improper synchronization. The attacker needs a valid local account and must win the timing window between two operations that share state inside the driver. Successful exploitation yields code execution or state manipulation at kernel privilege, which fulfills the confidentiality, integrity, and availability impact reflected in the CVSS vector.
Root Cause
The root cause is a race condition in NTFS handling logic where one code path can access a structure member before another path finishes initializing it. Under the race, the pointer field is NULL when the driver dereferences it. Microsoft has not published the specific function or field in the public advisory.
Attack Vector
Exploitation is local and requires authentication with low privileges. The attacker triggers concurrent file system operations, typically through crafted I/O request sequences against an NTFS volume, and races the vulnerable code path. The CVSS vector rates attack complexity as high because the attacker must reliably time the race to reach the dereference and convert it into privilege escalation rather than a bug check.
No public proof-of-concept exploit or CISA KEV entry exists for CVE-2025-49678 at the time of writing. See the Microsoft Security Update Guide entry for CVE-2025-49678 for vendor technical detail.
Detection Methods for CVE-2025-49678
Indicators of Compromise
- Unexpected BSOD events referencing ntfs.sys or KERNEL_MODE_EXCEPTION_NOT_HANDLED on hosts that host untrusted local users.
- Local user processes issuing high-frequency, concurrent NTFS I/O against the same handle or path immediately followed by privilege changes on that user's tokens.
- New services, scheduled tasks, or local administrator group membership created by a previously standard user account.
Detection Strategies
- Hunt for standard-user processes that spawn SYSTEM-level child processes without a legitimate elevation path such as UAC consent or service invocation.
- Correlate kernel crashes involving ntfs.sys with the local user session active on the host to spot exploitation attempts that fail the race.
- Baseline expected NTFS metadata operations per user and alert on burst patterns consistent with race window brute forcing.
Monitoring Recommendations
- Forward Windows System, Security, and kernel dump metadata to a central SIEM and retain sufficient history to reconstruct the process tree around suspected escalations.
- Enable Sysmon Event IDs 1, 10, and 11 to capture process creation, process access, and file create events on NTFS volumes.
- Track integrity level transitions on tokens and alert when a Medium-integrity process is later observed with a High or System-integrity child.
How to Mitigate CVE-2025-49678
Immediate Actions Required
- Deploy the July 2025 Microsoft security updates that address CVE-2025-49678 to all supported Windows client and server SKUs listed in the advisory.
- Prioritize multi-user systems, terminal servers, VDI hosts, and jump boxes where local low-privileged access is expected.
- Restrict interactive and Remote Desktop logon on sensitive hosts to reduce the population of accounts that can reach the local attack surface.
Patch Information
Microsoft has released fixes through its Security Update Guide. Consult the Microsoft Security Update Guide entry for CVE-2025-49678 for the specific KB articles and package identifiers that match each Windows build in your environment. Apply the corresponding cumulative update or monthly rollup and reboot to load the patched ntfs.sys.
Workarounds
- No official vendor workaround exists. Patching is the supported remediation path.
- Reduce exposure by limiting local logon rights and removing standard users from shared multi-tenant hosts until updates are deployed.
- Enforce application allowlisting to block unknown binaries that could carry an exploit for the race condition.
# Verify installed updates on a Windows host after patching
wmic qfe list brief /format:table
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 20
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
