CVE-2025-30385 Overview
CVE-2025-30385 is a use-after-free vulnerability in the Windows Common Log File System (CLFS) driver. An authorized local attacker can exploit the flaw to elevate privileges to SYSTEM. The weakness is tracked under CWE-416 and affects a broad range of Windows client and server releases, including Windows 10, Windows 11, and Windows Server versions from 2008 through 2025. Microsoft published guidance for the issue on May 13, 2025. Exploitation requires local access with low privileges and no user interaction.
Critical Impact
Successful exploitation yields SYSTEM-level privileges on any supported Windows host, enabling full compromise of the local operating system.
Affected Products
- Microsoft Windows 10 (1607, 1809, 21H2, 22H2)
- Microsoft Windows 11 (22H2, 23H2, 24H2)
- Microsoft Windows Server 2008, 2012, 2016, 2019, 2022, 2022 23H2, and 2025
Discovery Timeline
- 2025-05-13 - CVE-2025-30385 published to NVD
- 2025-05-13 - Microsoft released security update guidance via the Microsoft Security Update Advisory
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-30385
Vulnerability Analysis
The Common Log File System is a kernel-mode logging subsystem exposed through clfs.sys. It manages base log files (.blf) and container files used by applications and the operating system for transactional logging. CVE-2025-30385 is a use-after-free condition in this driver. A local attacker with a standard user account can trigger reuse of a freed kernel object during log file operations. Manipulating the freed memory allows the attacker to influence kernel execution flow. The result is arbitrary code execution in kernel mode and elevation to SYSTEM.
Root Cause
The root cause is improper lifetime management of an internal CLFS object. Under specific request sequences, the driver frees a structure while another code path still holds a reference to it. Subsequent access to that dangling pointer dereferences memory the attacker can reclaim and control. This class of defect is cataloged as CWE-416: Use After Free.
Attack Vector
The attack is local. The attacker must already be able to run code on the target as a standard user, for example through prior initial access, a compromised service account, or an interactive session. No user interaction is required. The attacker invokes CLFS APIs to open, manipulate, and race operations against a crafted base log file, driving the driver into the vulnerable state and then leveraging the freed allocation to hijack kernel execution.
No public proof-of-concept code, exploit module, or CISA Known Exploited Vulnerabilities listing was available for CVE-2025-30385 at the time of publication. Refer to the Microsoft Security Update Advisory for authoritative technical detail.
Detection Methods for CVE-2025-30385
Indicators of Compromise
- Creation of unusual .blf base log files or CLFS container files in writable user directories, followed by rapid open, close, and re-open sequences.
- Kernel bugchecks or crashes referencing clfs.sys on hosts running unpatched Windows builds.
- New SYSTEM-context processes spawned from a standard user session shortly after CLFS activity.
Detection Strategies
- Correlate low-privilege process activity with immediate SYSTEM-level child processes to surface local elevation attempts.
- Alert on abnormal invocation of CLFS APIs such as CreateLogFile, AddLogContainer, and AlignReservedLog from non-service accounts.
- Monitor Windows Error Reporting and crash telemetry for repeated clfs.sys faults, which frequently accompany exploitation attempts against this driver.
Monitoring Recommendations
- Ingest Sysmon Event ID 1 (process create) and Event ID 10 (process access) into your SIEM to build user-to-SYSTEM escalation detections.
- Track kernel driver load events (Event ID 6) and any tampering with clfs.sys or associated registry keys.
- Retain endpoint telemetry for at least 90 days to support retrospective hunts once exploitation techniques become public.
How to Mitigate CVE-2025-30385
Immediate Actions Required
- Apply the May 2025 Patch Tuesday updates from Microsoft to every affected Windows client and server SKU without delay.
- Prioritize multi-user systems, jump hosts, terminal servers, and developer workstations where local code execution by standard users is most likely.
- Audit local accounts and remove unnecessary interactive logon rights to reduce the pool of principals able to reach the vulnerable driver.
Patch Information
Microsoft addressed CVE-2025-30385 in the May 13, 2025 security updates. Refer to the Microsoft Security Update Advisory for the specific KB article and cumulative update that corresponds to each affected Windows build.
Workarounds
- No official workaround has been published by Microsoft; patching is the supported remediation.
- Restrict local logon and remote interactive access to trusted administrators until updates are deployed.
- Enforce application allowlisting to block unauthorized binaries from invoking CLFS APIs on high-value hosts.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
