CVE-2025-62470 Overview
CVE-2025-62470 is a heap-based buffer overflow [CWE-122] in the Windows Common Log File System (CLFS) Driver. The flaw allows an authenticated local attacker to corrupt kernel heap memory and elevate privileges to SYSTEM. Microsoft published the advisory on December 9, 2025, and it affects nearly every supported Windows client and Windows Server release, from Windows Server 2008 through Windows 11 25H2 and Windows Server 2025. Successful exploitation grants full confidentiality, integrity, and availability impact on the local host.
Critical Impact
An authorized local user can trigger a heap overflow in the CLFS kernel driver to gain SYSTEM-level privileges, enabling full compromise of the affected Windows host.
Affected Products
- Microsoft Windows 10 (1607, 1809, 21H2, 22H2)
- Microsoft Windows 11 (23H2, 24H2, 25H2)
- Microsoft Windows Server 2008, 2012, 2016, 2019, 2022, 2022 23H2, and 2025
Discovery Timeline
- 2025-12-09 - CVE-2025-62470 published to NVD with Microsoft security update guidance
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-62470
Vulnerability Analysis
The Common Log File System (CLFS.sys) is a general-purpose logging subsystem used by kernel-mode and user-mode components in Windows. CLFS has been a repeated source of local privilege escalation bugs because it parses complex Base Log File (.blf) structures directly in kernel memory.
This vulnerability is a heap-based buffer overflow inside the CLFS driver. When the driver processes attacker-controlled log metadata, it writes past the bounds of a pool allocation. The corrupted region resides in the kernel pool, so successful shaping of adjacent allocations can overwrite kernel objects and lead to arbitrary code execution in ring 0.
Root Cause
The root cause is improper validation of size or offset fields in log file records before they are copied into a heap-allocated kernel buffer. When a length field exceeds the destination allocation, the copy operation overflows the buffer and clobbers adjacent pool memory. This is a classic instance of [CWE-122: Heap-based Buffer Overflow] in a kernel driver.
Attack Vector
Exploitation requires local access and low-privileged authenticated execution on the target machine. An attacker runs code as a standard user, opens or creates a crafted CLFS log, and issues log I/O control operations that reach the vulnerable parsing path. No user interaction is required beyond executing the exploit binary. Because the vector is local, the flaw is most relevant as a post-compromise privilege escalation primitive following initial access via phishing, malicious documents, or supply-chain intrusion.
No public proof-of-concept or in-the-wild exploitation has been documented in the referenced advisory, and the CVE is not listed in the CISA Known Exploited Vulnerabilities catalog. Historical CLFS flaws such as CVE-2022-37969 and CVE-2023-28252 have seen rapid weaponization, so defenders should treat this issue with equivalent urgency.
Detection Methods for CVE-2025-62470
Indicators of Compromise
- Unexpected creation or modification of Base Log Files (.blf) or container files (.blf.blf) in user-writable directories such as %TEMP% or %LOCALAPPDATA%.
- Standard-user processes spawning SYSTEM-level child processes (for example, cmd.exe or powershell.exe running as NT AUTHORITY\SYSTEM).
- Kernel bug checks (BSOD) referencing CLFS.sys shortly after execution of an unknown binary.
Detection Strategies
- Hunt for anomalous handles to \Device\CLFS opened by non-service processes running under low-privileged user accounts.
- Alert on token privilege changes where a process token is replaced with the SYSTEM token immediately after CLFS API calls.
- Correlate .blf file creation events with subsequent parent-child process trees that show privilege elevation.
Monitoring Recommendations
- Enable kernel-mode event tracing for CLFS and forward the events to a centralized SIEM for long-term retention and correlation.
- Baseline expected callers of CLFS in the environment (Kernel Transaction Manager, TxF, TxR) and alert on outliers.
- Monitor Windows Event Log channels for driver crashes referencing CLFS immediately followed by suspicious process launches.
How to Mitigate CVE-2025-62470
Immediate Actions Required
- Apply the Microsoft security update referenced in the Microsoft CVE-2025-62470 Update advisory to every affected Windows client and server.
- Prioritize patching on multi-user systems, terminal servers, and virtual desktop infrastructure where local privilege escalation has the greatest blast radius.
- Restrict interactive logon and code execution rights for untrusted users on sensitive hosts.
Patch Information
Microsoft has released patches for all supported Windows versions listed in the advisory. Administrators should deploy the December 2025 cumulative security updates through Windows Update, Windows Server Update Services (WSUS), Microsoft Intune, or a supported third-party patch management platform. Refer to the Microsoft Security Response Center guidance for KB numbers per operating system build.
Workarounds
- No official workaround is documented. Enforce least-privilege policies and application allowlisting (for example, Windows Defender Application Control) to reduce the population of unknown binaries that can reach the CLFS driver.
- Segment and monitor legacy systems (Windows Server 2008, 2012) that cannot be patched immediately, and plan migration to a supported release.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
