CISA Warns of Windows Cloud Files Mini Filter 0-Day Vulnerability Exploited in Attacks

CISA has issued a critical alert regarding an actively exploited zero-day vulnerability impacting the Microsoft Windows Cloud Files Mini Filter Driver. Tracked as CVE-2025-62221, this flaw is a use-after-free vulnerability that allows authorized attackers to elevate their local privileges on compromised systems. This poses a significant risk to organizations running affected Windows systems and demands immediate remediation efforts. The vulnerability’s active exploitation in the wild underscores its severe nature, enabling attackers who have already gained initial access to escalate their control to system-level, potentially leading to a complete system compromise.

The use-after-free vulnerability class represents a dangerous memory safety issue where software attempts to access memory that has already been released. This particular flaw enables attackers to execute arbitrary code with elevated privileges, transforming an initial foothold into pervasive control. CISA emphasizes that this capability is especially concerning for enterprises, where an attacker could leverage an initial compromise into a full infrastructure takeover, impacting organizations across all sectors relying on Windows systems.

Reflecting the urgency and active exploitation, CISA added this vulnerability to its catalog on December 9, 2025. A mandatory remediation deadline has been set for December 30, 2025, highlighting the compressed timeline and the critical need for swift action. This rapid timeline reflects the severity and confirmed active exploitation of this flaw, which affects a broad spectrum of organizations across all sectors.

Organizations must prioritize applying all available Microsoft mitigations and patches as soon as possible. For agencies operating cloud services, strict adherence to BOD 22-01 guidance is mandatory. If immediate patching is not feasible, CISA recommends discontinuing the use of affected systems until remediation is available. IT teams are urged to monitor Microsoft security advisories for comprehensive guidance on patches and to implement updates promptly after testing confirms compatibility with critical systems. Furthermore, network defenders should enhance monitoring for unusual privilege escalation attempts and suspicious process behavior on Windows systems to detect and mitigate potential exploitation attempts.

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