Windows CLFS Driver Zero-Day CVE-2025-32701: Privilege Escalation in the Wild

Introduction

A critical zero-day vulnerability, CVE-2025-32701, in the Windows Common Log File System (CLFS) driver is actively exploited by threat actors, enabling them to escalate privileges to SYSTEM-level. This vulnerability significantly increases the risk of ransomware deployment and persistent compromise, demanding immediate attention and remediation.

Affected Systems and Versions

• Microsoft Windows systems utilizing the Common Log File System (CLFS) driver are affected.
• Specific affected versions include all supported Windows versions prior to the May 2025 security update.

Technical Information

CVE-2025-32701 results from a use-after-free (UAF) error (CWE-416) within the Windows CLFS driver. The vulnerability occurs when the driver improperly manages memory references after freeing a CLFS log stream object. Attackers exploit this flaw by:

1. Gaining initial local access.
2. Triggering specific log operations (e.g., CreateLogFile, AddLogContainer) to prematurely free memory.
3. Reclaiming the freed memory with attacker-controlled data via heap spraying.
4. Dereferencing the corrupted pointer, executing arbitrary code with SYSTEM privileges.

This exploit bypasses kernel protections like Kernel Address Space Layout Randomization (KASLR) due to predictable object layouts.

Patch Information

• Immediate patching to Microsoft's May 2025 security update (KB5058405/KB5058379) is essential.
• Patch details and downloads available at Microsoft Security Response Center.

Detection Methods

• Monitor for anomalous svchost.exe interactions with clfs.sys.
• Audit logs for unexpected CLFS API usage.
• Enable Windows Defender Attack Surface Reduction (ASR) rules to detect and block credential-stealing techniques.

Vendor Security History

Microsoft's CLFS driver has a concerning history of vulnerabilities, including CVE-2024-49138 and multiple others in 2024 and early 2025. These vulnerabilities have historically been exploited by ransomware groups, highlighting systemic security challenges within the CLFS component.

References

• Microsoft Advisory
• NVD Entry
• CISA Known Exploited Vulnerabilities Catalog
• Tenable Analysis
• HelpNet Security

Security teams must prioritize patching and monitoring to mitigate the significant risks posed by CVE-2025-32701.