CVE-2026-49795: Windows 10 1809 Privilege Escalation Flaw

CVE-2026-49795 Overview

CVE-2026-49795 is a use-after-free vulnerability [CWE-416] in the Windows Kernel that allows an authorized local attacker to elevate privileges. Microsoft assigned a CVSS 3.1 base score of 8.8, reflecting the scoped impact on confidentiality, integrity, and availability once exploited. The flaw affects a broad range of supported Windows client and server releases, including Windows 10, Windows 11, and Windows Server 2019 through 2025. Successful exploitation lets a low-privileged process obtain SYSTEM-level execution, giving an attacker full control of the host.

Critical Impact
A local attacker with valid credentials can trigger the kernel use-after-free to escalate to SYSTEM, enabling credential theft, tamper with security tooling, and full host compromise.

Affected Products

Microsoft Windows 10 (1809, 21H2, 22H2) across x86, x64, and ARM64 builds
Microsoft Windows 11 (24H2, 25H2, 26H1) across x64 and ARM64 builds
Microsoft Windows Server 2019, Server 2022, and Server 2025

Discovery Timeline

2026-07-14 - CVE-2026-49795 published to NVD
2026-07-16 - Last updated in NVD database

Technical Details for CVE-2026-49795

Vulnerability Analysis

The defect is a use-after-free condition in the Windows Kernel. The kernel frees a memory object while a reference to that object remains reachable through another code path. A subsequent operation dereferences the stale pointer, letting attacker-controlled data occupy the freed allocation.

Once the attacker sprays the freed slot with a crafted object, the kernel treats attacker data as a valid structure. This typically yields arbitrary read/write primitives in kernel space and enables token replacement or callback hijacking to achieve SYSTEM privileges. The scope change reflected in the CVSS vector indicates that impact crosses the user-to-kernel trust boundary.

Root Cause

The root cause is improper lifetime management of a kernel object [CWE-416]. Reference counting or lock ordering fails to keep the object alive for the duration of all concurrent operations. When one code path releases the allocation while another still holds a pointer, the second path operates on freed memory.

Attack Vector

Exploitation requires local access and low privileges, with no user interaction. An attacker running code as a standard user issues a specific sequence of system calls or IOCTLs that races the free with a subsequent dereference. Public technical details and proof-of-concept code are not available at the time of writing. See the Microsoft CVE-2026-49795 Advisory for vendor guidance.

Detection Methods for CVE-2026-49795

Indicators of Compromise

Unexpected nt! kernel bugchecks (Stop 0x3B, 0x50, 0xC4) originating from a user-launched process shortly before the crash
Standard-user processes suddenly running with NT AUTHORITY\SYSTEM token, especially spawning cmd.exe, powershell.exe, or lsass handles
New services, scheduled tasks, or drivers created immediately after a low-privileged process performed unusual NtDeviceIoControlFile activity

Detection Strategies

Hunt for token-swap behavior: a process whose parent ran as a normal user but whose current token integrity level is System or High
Correlate kernel crash telemetry from WER reports with the crashing user process to identify repeated exploitation attempts
Alert on unsigned or newly loaded kernel modules and on abnormal handle duplications targeting lsass.exe

Monitoring Recommendations

Ingest Windows Security, Sysmon, and kernel crash telemetry into a centralized SIEM or data lake for cross-host correlation
Track process integrity level transitions and parent-child anomalies on servers and privileged workstations
Baseline normal driver load events and alert on deviations, particularly following patch deployment windows

How to Mitigate CVE-2026-49795

Immediate Actions Required

Apply the Microsoft security update for CVE-2026-49795 to all affected Windows client and server builds
Prioritize patching multi-user systems, terminal servers, VDI hosts, and jump boxes where local access is common
Audit local account privileges and remove unnecessary interactive logon rights on servers
Enforce application control to block execution of unapproved binaries that could deliver an exploit payload

Patch Information

Microsoft has released fixes through the Microsoft Update channel. Consult the Microsoft CVE-2026-49795 Advisory for the specific KB articles and cumulative update identifiers that address each affected Windows version.

Workarounds

No vendor-supplied workaround is documented; patching is the required remediation
Restrict local logon and remote desktop access to trusted administrative accounts until updates are deployed
Enable Hypervisor-Protected Code Integrity (HVCI) and Credential Guard where supported to raise the cost of kernel exploitation

bash

# Verify installed cumulative update on Windows hosts
wmic qfe list brief /format:table

# PowerShell equivalent, filter for recent updates
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 10