CVE-2025-62454: 
vulnerability analysis and mitigation

CVE-2025-62454 is a heap-based buffer overflow vulnerability in the Windows Cloud Files Mini Filter Driver that allows an authorized (low-privileged) local attacker to elevate privileges on affected systems. It was disclosed and patched on December 9, 2025, as part of Microsoft's December 2025 Patch Tuesday security update cycle. Affected products span a wide range of Windows versions including Windows 10 (1809, 21H2, 22H2), Windows 11 (23H2, 24H2, 25H2), Windows Server 2019, Windows Server 2022 (including 23H2 edition), and Windows Server 2025. The vulnerability carries a CVSS v3.1 base score of 7.8 (High) (Microsoft MSRC, Tenable).

The root cause is a heap-based buffer overflow (CWE-122) in the Windows Cloud Files Mini Filter Driver (cldflt.sys), a kernel-mode driver responsible for supporting cloud-backed file placeholders (e.g., OneDrive on-demand sync). An attacker with low-privileged local access can trigger the overflow through crafted interactions with the driver, potentially corrupting heap memory in kernel space to redirect execution flow and gain elevated privileges. The attack vector is local, requires low privileges, no user interaction, and has low attack complexity, making it straightforward to exploit once an attacker has a foothold on the system. No public proof-of-concept code has been identified at the time of disclosure (Microsoft MSRC, Qualys Blog).

Successful exploitation allows a local attacker to escalate from a standard user account to SYSTEM-level privileges, resulting in high confidentiality, integrity, and availability impact across the affected host. With SYSTEM-level access, an attacker can install malware, modify or delete system files, access sensitive credentials and data, disable security controls, and pivot laterally to other systems on the network. The broad scope of affected Windows versions — spanning consumer and enterprise desktop and server editions — significantly widens the potential attack surface (Microsoft MSRC, Tenable).

Microsoft released patches on December 9, 2025, as part of the December 2025 Patch Tuesday update. Organizations should apply the following minimum build versions: Windows 10 21H2 → 10.0.19044.6691; Windows 10 22H2 → 10.0.19045.6691; Windows 10 1809 → 10.0.17763.8146; Windows 11 23H2 → 10.0.22631.6345; Windows 11 24H2 → 10.0.26100.7392; Windows 11 25H2 → 10.0.26200.7392; Windows Server 2019 → 10.0.17763.8146; Windows Server 2022 → 10.0.20348.4467; Windows Server 2022 23H2 → 10.0.25398.2025; Windows Server 2025 → 10.0.26100.7392. As interim mitigations, organizations should enforce the principle of least privilege to limit the number of accounts that could be used to trigger the vulnerability, and monitor for suspicious privilege escalation activity (Microsoft MSRC, Qualys Blog).

CVE-2025-62454 was covered as part of broader December 2025 Patch Tuesday roundups by multiple security vendors and researchers. Tenable, Qualys, Sophos, Talos Intelligence, and Zero Day Initiative all included it in their monthly patch review summaries, noting it as a high-severity local privilege escalation without active exploitation (Tenable, Sophos, ZDI). Community discussion on Reddit and security news outlets focused primarily on the three zero-days patched in the same update cycle, with CVE-2025-62454 receiving less individual attention due to the absence of a public PoC or active exploitation (BleepingComputer).