CVE-2022-24521
Microsoft Windows CLFS Driver Privilege Escalation Vulnerability
Description
CVE-2022-24521 is a privilege escalation vulnerability in the Microsoft Windows Common Log File System (CLFS) Driver that allows an authenticated local attacker to gain SYSTEM-level privileges on affected systems. The vulnerability exploits a flaw in how the CLFS driver processes log files, enabling an attacker with standard user access to escalate their privileges to the highest level on the operating system. CISA has added CVE-2022-24521 to the Known Exploited Vulnerabilities catalog, confirming active exploitation in the wild. With an EPSS score of 0.26% (96.8th percentile), this vulnerability poses a significant post-compromise threat for organizations running unpatched Windows systems.
KEV Information
CVSS Score
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| microsoft | windows 10 1507 | < 10.0.10240.19265 |
| microsoft | windows 10 1607 | < 10.0.14393.5066 |
| microsoft | windows 10 1809 | <= 10.0.17763.2803 |
| microsoft | windows 10 1909 | < 10.0.18363.2212 |
| microsoft | windows 10 20h2 | < 10.0.19042.1645 |
| microsoft | windows 10 21h1 | < 10.0.19043.1645 |
| microsoft | windows 10 21h2 | < 10.0.19044.1645 |
| microsoft | windows 11 21h2 | < 10.0.22000.613 |
| microsoft | windows 7 | - |
| microsoft | windows 8.1 | - |
| microsoft | windows rt 8.1 | - |
| microsoft | windows server 2008 | r2 |
| microsoft | windows server 2012 | -; r2 |
| microsoft | windows server 2016 | < 10.0.14393.5066 |
| microsoft | windows server 2019 | < 10.0.17763.2803 |
| microsoft | windows server 2022 | < 10.0.20348.643 |
| microsoft | windows server 20h2 | < 10.0.19042.1645 |
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2022-24521(Patch, Vendor Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2022-24521(US Government Resource)
Weakness Type
CWE-269: Improper Privilege Management
CWE-269 describes a weakness where software does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control. In CVE-2022-24521, the Windows CLFS driver fails to properly manage privileges when processing certain log file operations, allowing a locally authenticated attacker to elevate their permissions from a standard user to SYSTEM, the highest privilege level on a Windows system.
Learn more: CWE-269 — Improper Privilege Management
Impact Analysis
CVE-2022-24521 allows an authenticated attacker to escalate from standard user privileges to SYSTEM level, granting complete control over the affected Windows system. Once SYSTEM privileges are obtained, the attacker can access all files and registry keys, install rootkits and persistent backdoors, dump credential stores including LSASS memory, disable security software, and modify audit configurations to cover their tracks. While the vulnerability requires local or remote desktop access with valid credentials, it is a critical post-exploitation tool that transforms an initial foothold into full system compromise. The EPSS score of 0.26% (96.8th percentile) and KEV listing confirm this vulnerability is actively used by threat actors in real-world attack chains.
Exploit Maturity
CVE-2022-24521 is listed in the CISA Known Exploited Vulnerabilities catalog, confirming active exploitation against Windows systems. The EPSS score of 0.26% (96.8th percentile) indicates a high probability of exploitation, and the CLFS driver has been a recurring target for privilege escalation exploits. Multiple CLFS vulnerabilities have been exploited in the wild in recent years, indicating that attackers have developed mature exploitation techniques for this Windows subsystem.
Remediation
- Apply Microsoft security updates immediately as required by CISA KEV: install the April 2022 Patch Tuesday updates that address CVE-2022-24521 in the Windows CLFS driver.
- Prioritize patching on systems where users have interactive login access, as the vulnerability requires local authentication to exploit.
- Implement endpoint detection and response (EDR) monitoring for suspicious CLFS driver activity, particularly unusual log file operations or SYSTEM token manipulation.
- Apply the principle of least privilege to limit the number of user accounts with interactive login capabilities on servers and critical workstations.
- Monitor Windows Event Logs for unexpected privilege escalation events, new service installations, or LSASS access attempts that may indicate post-exploitation activity.
Technical Details
CVE-2022-24521 is a privilege escalation vulnerability in the Windows Common Log File System (CLFS) driver (clfs.sys), which handles transaction logging for NTFS and other Windows subsystems. The vulnerability stems from improper handling of specially crafted CLFS log files or base log file (BLF) metadata, allowing an authenticated attacker to trigger a condition that grants SYSTEM-level privileges. The attack requires local access with at least standard user permissions, and exploitation involves manipulating CLFS data structures to corrupt memory in a way that enables token replacement or privilege escalation through kernel-mode code execution. The CLFS driver operates at the kernel level, making exploitation particularly impactful as it bypasses all user-mode security controls.
Frequently Asked Questions
Is CVE-2022-24521 being actively exploited?
Yes. CVE-2022-24521 is listed in the CISA Known Exploited Vulnerabilities catalog, confirming active exploitation against Windows systems. The CLFS driver has been a recurring target for attackers, with multiple vulnerabilities exploited in this component in recent years.
What products are affected by CVE-2022-24521?
CVE-2022-24521 affects the Windows Common Log File System (CLFS) Driver across multiple supported versions of Microsoft Windows, including Windows 10, Windows 11, and Windows Server editions.
How do I fix CVE-2022-24521?
Install the April 2022 Microsoft security updates that patch the CLFS driver vulnerability. Prioritize systems with interactive user access, as the vulnerability requires local authentication.
How severe is CVE-2022-24521?
CVE-2022-24521 is a high-severity privilege escalation vulnerability that allows standard users to gain SYSTEM privileges. While it requires local authentication, it is a critical post-exploitation tool actively used in attack chains to achieve full system compromise.
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