CISA Alerts on Actively Exploited Windows Cloud Files Mini Filter 0-Day

The Cybersecurity and Infrastructure Security Agency has added a critical privilege escalation vulnerability in Microsoft Windows to its Known Exploited Vulnerabilities catalog, warning organizations of active exploitation attempts targeting the Windows Cloud Files Mini Filter Driver.

The vulnerability, tracked as CVE-2025-62221, is a use-after-free flaw in the Cloud Files Mini Filter Driver that allows authorized attackers to elevate privileges locally.

According to the CISA alert issued on December 9, 2025, organizations must prioritize patching efforts immediately, with a mandatory remediation deadline of December 30, 2025, under BOD 22-01 guidance.

Vulnerability Overview and Impact

The use-after-free vulnerability stems from improper memory management in the Windows Cloud Files Mini Filter Driver, a kernel-level component that manages cloud-integrated file systems.

An attacker with local access could exploit this flaw to gain elevated system privileges, potentially resulting in a complete system compromise.

While CISA has not confirmed active ransomware campaigns exploiting this vulnerability, the ongoing exploitation warrants immediate attention.

The vulnerability affects organizations relying on Windows cloud integration features, particularly those using OneDrive, SharePoint, or other cloud-based file synchronization services.

The severity of local privilege escalation exploits means that malware or a compromised user account with local system access can escalate to administrator-level permissions.

CISA recommends that organizations take immediate action by following the following prioritized steps.

First, apply vendor-provided security patches and mitigations according to Microsoft’s official guidance as soon as they become available.

Second, implement BOD 22-01 compliance measures for cloud service environments, including enhanced monitoring and access controls.

Third, organizations unable to implement mitigations should discontinue use of affected Windows systems or isolate them from network environments.

Security teams should also conduct threat assessments to determine if exploitation attempts have occurred within their environments.

Monitor for suspicious local privilege escalation activities and review authentication logs for unauthorized account elevation.

The December 30, 2025, deadline provides a three-week remediation window, reflecting the active exploitation status.

Organizations should prioritize this vulnerability above other pending patches and allocate resources accordingly.

CVE ID	Vulnerability Type	Affected Component	Attack Type	Severity	Due Date
CVE-2025-62221	Use After Free	Windows Cloud Files Mini Filter Driver	Local Privilege Escalation	Critical	2025-12-30

Microsoft has been notified and is preparing official security updates. Organizations should monitor the Microsoft Security Response Center for patch releases and implementation guidance throughout the remediation window.

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