CVE-2023-28252: Windows 10 Privilege Escalation Vulnerability

CVE-2023-28252 Overview

CVE-2023-28252 is a critical elevation of privilege vulnerability affecting the Windows Common Log File System (CLFS) driver (clfs.sys). This kernel-mode driver is responsible for managing high-performance transaction logging on Windows systems and is present across virtually all modern Windows operating systems. When successfully exploited, this vulnerability allows a local attacker with limited privileges to escalate to SYSTEM-level access, effectively gaining complete control over the affected machine.

Critical Impact

This vulnerability is actively exploited in the wild and has been added to CISA's Known Exploited Vulnerabilities catalog. Attackers can leverage this flaw to escape application sandboxes, deploy ransomware with elevated permissions, or establish persistent footholds on compromised systems.

Affected Products

• Microsoft Windows 10 (versions 1507, 1607, 1809, 20H2, 21H2, 22H2)
• Microsoft Windows 11 (versions 21H2, 22H2)
• Microsoft Windows Server 2008 (SP2 and R2 SP1)
• Microsoft Windows Server 2012 and 2012 R2
• Microsoft Windows Server 2016
• Microsoft Windows Server 2019
• Microsoft Windows Server 2022

Discovery Timeline

• April 11, 2023 - CVE-2023-28252 published to NVD
• October 28, 2025 - Last updated in NVD database

Technical Details for CVE-2023-28252

Vulnerability Analysis

The vulnerability resides in the Windows Common Log File System driver, a kernel-mode component that provides general-purpose logging functionality for Windows applications and services. The CLFS driver processes Base Log File (BLF) structures that contain metadata about transaction logs. A heap-based buffer overflow condition (CWE-122) occurs when the driver improperly validates certain fields within maliciously crafted BLF structures, resulting in out-of-bounds write operations (CWE-787) in kernel memory.

The flaw can be triggered by a local user with standard privileges who can create or manipulate CLFS log files. By carefully crafting the contents of a BLF file with specific malformed metadata, an attacker can corrupt adjacent kernel memory structures. This memory corruption can be leveraged to overwrite critical kernel objects, such as token structures, enabling the attacker to modify their process's security context and elevate privileges to SYSTEM.

Root Cause

The root cause of this vulnerability is improper bounds checking in the CLFS driver when parsing Base Log File structures. Specifically, the driver fails to adequately validate offset and size fields within BLF metadata before performing memory operations. This lack of input validation allows an attacker to specify values that cause the driver to write beyond allocated buffer boundaries in kernel pool memory, creating a heap-based buffer overflow condition that can be exploited for privilege escalation.

Attack Vector

The attack vector is local, requiring an attacker to have initial access to the target system with the ability to execute code as a low-privileged user. The exploitation process involves:

1. Creating a malicious CLFS Base Log File with crafted metadata containing invalid offset or size values
2. Triggering the CLFS driver to process the malformed BLF structure through standard Windows API calls
3. Exploiting the resulting heap overflow to corrupt kernel memory structures
4. Manipulating token objects or other security-critical kernel structures to escalate privileges

The attacker can weaponize this vulnerability to escape application sandboxes, bypass User Account Control (UAC), or gain SYSTEM privileges from a standard user context. The vulnerability has been observed in use by ransomware operators and advanced threat actors as part of their attack chains.

Detection Methods for CVE-2023-28252

Indicators of Compromise

• Unusual creation or modification of .blf files in unexpected directories or by unauthorized processes
• Process crashes or unexpected termination of services related to CLFS operations
• Evidence of privilege escalation events where standard user processes spawn SYSTEM-level child processes
• Memory corruption artifacts or crash dumps indicating heap corruption in clfs.sys

Detection Strategies

• Monitor for suspicious API calls to CLFS-related functions such as CreateLogFile, CreateLogMarshallingArea, and related logging APIs from untrusted processes
• Deploy endpoint detection rules to identify known exploit payloads targeting CVE-2023-28252
• Implement kernel crash analysis to detect exploitation attempts that result in system instability
• Use behavioral detection to identify processes that suddenly gain elevated privileges without legitimate elevation mechanisms

Monitoring Recommendations

• Enable Windows Event logging for Security events, particularly Event ID 4688 (Process Creation) with command line auditing to track process lineage
• Configure SentinelOne to monitor for kernel exploitation behaviors and privilege escalation patterns
• Implement file integrity monitoring for system directories to detect unauthorized BLF file creation
• Review Windows Error Reporting data for clfs.sys-related crashes that may indicate exploitation attempts

How to Mitigate CVE-2023-28252

Immediate Actions Required

• Apply the April 2023 Microsoft security updates immediately on all affected Windows systems
• Prioritize patching for internet-facing systems and high-value assets that may be targeted by ransomware operators
• Review endpoint detection logs for any indicators of prior exploitation attempts
• Implement application control policies to restrict execution of unauthorized binaries

Patch Information

Microsoft released security updates addressing CVE-2023-28252 as part of their April 2023 Patch Tuesday release. The official advisory and patches are available through the Microsoft Security Update Guide. Given the active exploitation of this vulnerability, organizations should treat this patch as emergency priority. The vulnerability has been catalogued by CISA in their Known Exploited Vulnerabilities Catalog, mandating federal agencies to remediate by specific deadlines.

Workarounds

• Restrict local logon rights to only authorized users to reduce the attack surface
• Implement strict application whitelisting to prevent execution of exploit code
• Deploy SentinelOne's endpoint protection with behavioral AI to detect and block exploitation attempts
• Consider implementing virtualization-based security features such as Hypervisor-Protected Code Integrity (HVCI) where supported

# Verify patch status using PowerShell
Get-HotFix | Where-Object { $_.HotFixID -match "KB5025221|KB5025224|KB5025228|KB5025230|KB5025239" }

# Check CLFS driver version to confirm patched state
Get-Item C:\Windows\System32\drivers\clfs.sys | Select-Object -ExpandProperty VersionInfo