CVE-2024-49090: Windows 10 Privilege Escalation Flaw

CVE-2024-49090 Overview

CVE-2024-49090 is an elevation of privilege vulnerability in the Windows Common Log File System (CLFS) driver. The flaw affects supported releases of Windows 10, Windows 11, and Windows Server from Server 2008 through Server 2025. An authenticated local attacker can exploit the driver to gain SYSTEM-level privileges on the affected host. The issue is tracked under CWE-822: Untrusted Pointer Dereference and was published to the National Vulnerability Database on December 12, 2024.

Critical Impact
Successful exploitation grants an attacker full SYSTEM privileges, providing complete control over confidentiality, integrity, and availability on the host.

Affected Products

Microsoft Windows 10 (1507, 1607, 1809, 21H2, 22H2)
Microsoft Windows 11 (22H2, 23H2, 24H2)
Microsoft Windows Server 2008, 2012, 2012 R2, 2016, 2019, 2022, 2022 23H2, and 2025

Discovery Timeline

2024-12-12 - CVE-2024-49090 published to NVD
2025-01-08 - Last updated in NVD database

Technical Details for CVE-2024-49090

Vulnerability Analysis

The Common Log File System (clfs.sys) is a kernel-mode driver that provides a high-performance, general-purpose logging service used by both kernel and user-mode components. CVE-2024-49090 resides in the driver and allows an authenticated local user to escalate privileges. The vulnerability is categorized as an untrusted pointer dereference ([CWE-822]), where the driver operates on a pointer derived from attacker-controlled input without sufficient validation.

Because CLFS executes in kernel context, any memory corruption or controlled dereference inside the driver translates directly into kernel-level code execution. Successful exploitation yields full SYSTEM privileges and produces high impact across confidentiality, integrity, and availability.

Root Cause

The root cause involves improper validation of a pointer used by CLFS when processing log file structures. When the driver dereferences a pointer influenced by attacker-supplied data, the kernel reads or writes from an attacker-controlled address. This primitive can be leveraged to corrupt kernel objects or token structures, ultimately enabling the local attacker to elevate the privileges of an existing process.

Attack Vector

The attack vector is local. An attacker who has already obtained low-privilege code execution on the target, for example through phishing or a foothold from another exploit chain, can invoke crafted CLFS operations to trigger the vulnerable code path. User interaction is not required, and the attack complexity is low. CLFS vulnerabilities have historically been chained with initial access malware to escape sandboxes and obtain SYSTEM privileges before deploying ransomware or persistence mechanisms.

No public proof-of-concept exploit and no confirmed in-the-wild exploitation are listed for this CVE at the time of publication. Refer to the Microsoft Security Update Guide for CVE-2024-49090 for vendor technical details.

Detection Methods for CVE-2024-49090

Indicators of Compromise

Creation of unexpected .blf or CLFS log files in user-writable directories such as %TEMP% or %LOCALAPPDATA% by non-system processes.
Unprivileged processes spawning child processes that run as NT AUTHORITY\SYSTEM shortly after CLFS API activity.
Abnormal kernel crashes or bug checks referencing clfs.sys on hosts that did not previously exhibit driver instability.

Detection Strategies

Monitor process token elevation events where a medium or low integrity process gains SYSTEM integrity without an explicit UAC prompt or service launch.
Hunt for user-mode binaries calling CreateLogFile, AddLogContainer, or related CLFS APIs in rapid succession from non-standard image paths.
Correlate Windows Defender or EDR kernel telemetry indicating tampering with the EPROCESS token field against the originating process tree.

Monitoring Recommendations

Enable Windows kernel auditing and ship Sysmon Event ID 1, 10, and 25 telemetry to a central SIEM for behavioral correlation.
Track patch deployment status for the December 2024 Windows cumulative updates across all endpoints and servers.
Baseline normal CLFS activity per host so anomalous log container creation by user-mode processes generates alerts.

How to Mitigate CVE-2024-49090

Immediate Actions Required

Apply the December 2024 Microsoft security updates referenced in the MSRC advisory for CVE-2024-49090 on all affected Windows and Windows Server systems.
Prioritize patching of multi-user systems, terminal servers, developer workstations, and any host where low-privilege users can execute code.
Restrict local logon rights and remove unnecessary interactive accounts on servers to reduce the population of users able to trigger the vulnerable code path.

Patch Information

Microsoft addressed CVE-2024-49090 in the December 2024 Patch Tuesday release. Fixed builds are published per Windows version on the Microsoft Security Update Guide. Administrators should validate that the cumulative update is installed on every supported SKU listed under affected products, including legacy releases such as Windows Server 2008 SP2 and Server 2008 R2 SP1 covered under Extended Security Updates.

Workarounds

No official vendor workaround replaces installing the security update; mitigations are limited to reducing local attacker capability.
Enforce application allowlisting with Windows Defender Application Control or AppLocker to block unsigned local executables.
Apply least-privilege principles and remove standard users from systems that handle sensitive workloads until patching is complete.

bash

# Verify the December 2024 cumulative update is installed
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 10

# Confirm clfs.sys file version after patching
Get-Item C:\Windows\System32\drivers\clfs.sys | Select-Object VersionInfo