CVE-2025-29824

CVE-2025-29824 is a use-after-free flaw (CWE-416) in the Windows Common Log File System (CLFS) kernel driver, scored 7.8 (High) with a local attack vector, low privileges required, and no user interaction. An authorized local attacker can trigger it by interacting with CLFS-managed log files in a way that references freed kernel memory. Successful exploitation elevates the attacker's local privileges, typically to SYSTEM, providing full control of the host that can be chained into ransomware deployment or lateral movement. Any unpatched system running the listed Windows 10, Windows 11, or Windows Server versions is affected. The flaw was exploited as a zero-day — reportedly by Play ransomware — before Microsoft shipped fixes in the April 2025 Patch Tuesday release; it was added to CISA's KEV catalog on 2025-04-08 with known ransomware use, and EPSS estimates a 13.9% probability of continued exploitation over 30 days (96th percentile).

What to do: Apply Microsoft's April 2025 Patch Tuesday security updates for your Windows version immediately — the vendor update is the only complete fix, and the flaw is on the KEV list with known ransomware use, so prioritize servers and endpoints used by privileged users. Until patched, limit untrusted local code execution and review hosts for post-exploitation privilege escalation; public detection and mitigation scripts (e.g., Vicarius) are available to help hunt for exploitation. Federal agencies must apply the vendor mitigations per BOD 22-01 deadlines or discontinue use of affected versions.