CVE-2025-29824
Microsoft Windows Common Log File System (CLFS) Driver Use-After-Free Vulnerability
Description
CVE-2025-29824 is a high-severity use-after-free vulnerability in the Windows Common Log File System (CLFS) Driver that allows a local attacker with low privileges to escalate to SYSTEM-level access. This privilege escalation vulnerability affects virtually all supported versions of Microsoft Windows, from Windows 10 through Windows Server 2025. With a CVSS v3.1 score of 7.8 and confirmed use in ransomware campaigns, CVE-2025-29824 was added to CISA's Known Exploited Vulnerabilities catalog with a remediation deadline of April 29, 2025. The CLFS driver has been a recurring target for ransomware operators, and this vulnerability continues the pattern of exploiting Windows kernel components for privilege escalation in active attack chains.
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 | < 10.0.10240.20978 |
| microsoft | windows 10 1607 | < 10.0.14393.7969 |
| microsoft | windows 10 1809 | < 10.0.17763.7136 |
| microsoft | windows 10 21h2 | < 10.0.19044.5737 |
| microsoft | windows 10 22h2 | < 10.0.19045.5737 |
| microsoft | windows 11 22h2 | < 10.0.22621.5189 |
| microsoft | windows 11 23h2 | < 10.0.22631.5189 |
| microsoft | windows 11 24h2 | < 10.0.26100.3775 |
| microsoft | windows server 2008 | -; r2 |
| microsoft | windows server 2012 | -; r2 |
| microsoft | windows server 2016 | < 10.0.14393.7969 |
| microsoft | windows server 2019 | < 10.0.17763.7136 |
| microsoft | windows server 2022 | < 10.0.20348.3453 |
| microsoft | windows server 2022 23h2 | < 10.0.25398.1551 |
| microsoft | windows server 2025 | < 10.0.26100.3775 |
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-29824(Vendor Advisory)
- https://www.vicarius.io/vsociety/posts/cve-2025-29824-windows-common-log-file-system-driver-elevation-of-privilege-vulnerability-detection-script(Exploit, Third Party Advisory)
- https://www.vicarius.io/vsociety/posts/cve-2025-29824-windows-common-log-file-system-driver-elevation-of-privilege-vulnerability-mitigation-script(Exploit, Third Party Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-29824(US Government Resource)
Weakness Type
CWE-416: Use After Free
CVE-2025-29824 is classified under CWE-416 (Use After Free), a memory corruption weakness where a program continues to reference memory after it has been freed. In the Windows CLFS driver, a specific code path frees a memory object but retains a reference to it, allowing an attacker to manipulate the freed memory region before the dangling reference is used again. By carefully controlling the contents of the reallocated memory, an attacker can hijack execution flow to achieve SYSTEM-level privilege escalation.
Learn more: CWE-416 — Use After Free
Impact Analysis
CVE-2025-29824 carries a CVSS v3.1 base score of 7.8 (High) with maximum impact across confidentiality, integrity, and availability. The vulnerability requires local access (AV:L) with low privileges (PR:L) and no user interaction (UI:N), making it highly practical for post-initial-access exploitation. Confidentiality, integrity, and availability are all rated High because successful exploitation grants SYSTEM-level privileges, giving the attacker complete control over the compromised Windows system. This includes the ability to access all files, install persistent backdoors, disable security software, and encrypt data for ransomware operations. The EPSS score of 0.5% at the 64th percentile indicates early-stage exploitation tracking, but the confirmed ransomware association makes this vulnerability exceptionally dangerous. Ransomware operators are known to exploit this vulnerability, using it as a critical step in attack chains where initial access through phishing or other vectors is followed by CLFS-based privilege escalation to deploy ransomware with maximum system access.
Exploit Maturity
CVE-2025-29824 demonstrates high exploit maturity with confirmed active exploitation in ransomware campaigns. CISA has added this vulnerability to the Known Exploited Vulnerabilities catalog, and the ransomware association is classified as Known, indicating direct use by ransomware operators. Public exploit code and detection scripts are available via Vicarius vSociety and Vicarius vSociety. The EPSS score of 0.5% at the 64th percentile reflects early tracking, but the real-world deployment in ransomware operations demonstrates that weaponized exploits are in active use. The Windows CLFS driver has been a repeated target for privilege escalation exploits, with multiple previous CVEs (including CVE-2022-24521 and CVE-2023-28252) following the same pattern of CLFS vulnerabilities being exploited in ransomware attack chains.
Remediation
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Apply Microsoft security updates immediately. Install the April 2025 Patch Tuesday updates for all affected Windows versions. Specific fixed builds include Windows 10 1507 (10.0.10240.20978+), Windows 10 1607 (10.0.14393.7969+), Windows 10 1809 (10.0.17763.7136+), Windows 11 24H2 (10.0.26100.3775+), and corresponding Windows Server versions. Consult the Microsoft Security Update Guide for the complete list.
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Prioritize patching of systems accessible to standard users since the vulnerability requires only low-level privileges. Domain-joined workstations, terminal servers, and virtual desktop infrastructure (VDI) environments are high-priority targets where compromised user accounts could leverage this vulnerability.
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Deploy endpoint detection and response (EDR) rules to detect CLFS driver exploitation attempts. Monitor for suspicious processes creating or manipulating CLFS log files (.blf files), unexpected SYSTEM-level process spawning from low-privilege contexts, and known CLFS exploitation patterns.
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Review systems for indicators of compromise associated with ransomware campaigns targeting CLFS vulnerabilities. Look for unexpected .blf file creation in temp directories, suspicious privilege escalation events in Windows Security logs (Event ID 4672, 4688), and lateral movement patterns following initial access.
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Implement least privilege and application control policies. Restrict users to the minimum necessary privileges, deploy application whitelisting to prevent unauthorized executables, and enable Attack Surface Reduction (ASR) rules in Microsoft Defender to limit exploit techniques.
Technical Details
CVE-2025-29824 is a use-after-free vulnerability in the Windows Common Log File System (CLFS) driver, a kernel-mode component responsible for managing transactional log files. The CVSS v3.1 vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H confirms a locally exploitable flaw with low complexity that achieves full impact on all CIA dimensions. The CLFS driver manages base log files (.blf) and their associated metadata containers. The use-after-free condition occurs when the driver frees a kernel object during a specific operation but retains a stale pointer that is subsequently dereferenced. An attacker with low privileges can trigger this condition by crafting specific CLFS log file operations, then perform a heap spray to place controlled data at the freed memory location. When the dangling pointer is dereferenced, the attacker-controlled data is treated as a valid kernel object, enabling arbitrary kernel memory writes. This write primitive is then leveraged to overwrite process token privileges, escalating from a standard user to SYSTEM. The vulnerability affects all versions of the CLFS driver across Windows 10, Windows 11, and Windows Server 2008 through 2025.
Frequently Asked Questions
Is CVE-2025-29824 being actively exploited?
Yes. CISA has confirmed active exploitation and has classified the ransomware association as Known, meaning ransomware operators are actively using this vulnerability. The CLFS driver is a well-known target for privilege escalation in ransomware attack chains.
What products are affected by CVE-2025-29824?
CVE-2025-29824 affects virtually all supported versions of Microsoft Windows, including Windows 10 (1507, 1607, 1809, 21H2, 22H2), Windows 11 (22H2, 23H2, 24H2), and Windows Server 2008 through Windows Server 2025.
How do I fix CVE-2025-29824?
Apply the April 2025 Microsoft security updates for all affected Windows systems. This is the only complete fix. As an interim measure, monitor for CLFS exploitation indicators and restrict low-privilege user access where possible.
How severe is CVE-2025-29824?
CVE-2025-29824 has a CVSS score of 7.8 (High). While it requires local access, its confirmed use in ransomware operations, low exploitation complexity, and ability to grant SYSTEM privileges make it an extremely dangerous vulnerability that should be patched with the highest priority.
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