Hot on the heels of CVE-2025-66516, the maximum-severity Apache Tika XXE vulnerability, a couple of other security flaws have emerged in Windows products. In its December 2025 security update, Microsoft addressed 57 vulnerabilities, including two zero-days, CVE-2025-62221 and CVE-2025-54100.

Microsoft’s technologies underpin a vast share of the global digital infrastructure, making the security of its ecosystem especially critical. The 2025 BeyondTrust Microsoft Vulnerabilities Report notes that 2024 set a new record with 1,360 disclosed Microsoft vulnerabilities—an 11% jump from the previous year—with Elevation of Privilege (EoP) and RCE issues standing out as the most severe. That trend continued into 2025, with Tenable noting that Microsoft delivered patches for 1,129 CVEs in 2025—the second consecutive year the company exceeded the thousand-vulnerability threshold. In the December 2025 Patch Tuesday rollout, EoP flaws made up half of all addressed vulnerabilities, with RCE vulnerabilities following at roughly one-third (33.9%). The above-mentioned zero-days addressed in the December 2025 Patch Tuesday also fit into these threat categories. 

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CVE-2025-62221and CVE-2025-54100 Analysis

Microsoft is wrapping up the year by releasing patches for 57 security vulnerabilities in Windows products covered in its December 2025 security update release, including two zero-days with a CVSS score of 7.8, CVE-2025-62221 and CVE-2025-54100.

The actively exploited flaw, CVE-2025-62221, is a use-after-free elevation of privilege vulnerability in the Windows Cloud Files Mini Filter Driver that allows an authenticated local attacker to escalate privileges to SYSTEM. By exploiting this flaw, adversaries can gain full control of affected Windows systems without user interaction, though local access is required.

The vendor has confirmed 2025-62221 active exploitation in the wild; however, specific attack methods remain undisclosed. The vulnerability impacts systems with the Cloud Files minifilter, which is present even if apps like OneDrive, Google Drive, or iCloud aren’t installed. 

Due to the increasing exploitation risks, CISA has recently added CVE-2025-62221 to its KEV catalog, requiring Federal Civilian Executive Branch agencies to apply the update by December 30, 2025. 

Another zero-day, CVE-2025-54100, is an RCE flaw in Windows PowerShell that allows unauthenticated attackers to run arbitrary code if they can get a user to execute a crafted PowerShell command, for instance, via Invoke-WebRequest.

The risk becomes more pronounced when paired with common social-engineering tactics: adversaries could trick a user or administrator into running a PowerShell snippet that retrieves malicious content from a remote server, triggering a parsing bug and enabling code execution or implant delivery. Although the issue is publicly known, Microsoft reports no active exploitation and currently rates the likelihood of exploitation as low. The flaw requires no privileges but does rely on user interaction, making social engineering the most probable attack path.

As potential  2025-62221 and CVE-2025-54100 mitigation measures, organizations that rely on the corresponding Windows products are urged to apply the patches immediately. With SOC Prime’s AI-Native Detection Intelligence Platform, SOC teams can source detection content from the largest and up-to-date repository, seamlessly adopt the full pipeline from detection to simulation into their security processes, orchestrate workflows in their natural language, and smoothly navigate the ever-changing threat landscape while strengthening defenses at scale.