Microsoft today pushed updates to fix at least 56 security flaws in its Windows operating systems and supported software, concluding 2025 with a significant security release. This final Patch Tuesday of the year addresses one zero-day vulnerability that is already actively being exploited in the wild, alongside two other publicly disclosed vulnerabilities that have captured the attention of security researchers. This latest batch of patches arrives after a year that saw a notable increase in the sheer volume of vulnerabilities addressed by Microsoft, underscoring the ever-evolving threat landscape.

The scope of Microsoft’s security efforts in 2025 has been substantial. Despite a perceived lull in the number of individual Patch Tuesday releases in the preceding months, the cumulative total of patched vulnerabilities for the year reached a formidable 1,129. This represents an 11.9% increase compared to the 2024 calendar year, marking the second consecutive year that Microsoft has surpassed the thousand-vulnerability threshold and the third time in the company’s history that such a high volume of security fixes has been deployed. Satnam Narang, a prominent figure at Tenable, a leading cybersecurity firm, highlighted this trend, emphasizing the continuous effort required to maintain a secure computing environment.

The most pressing vulnerability addressed in this December update is CVE-2025-62221, a critical zero-day flaw that allows for privilege escalation. This weakness impacts Windows 10 and all subsequent editions of the operating system. The vulnerability lies within a core component known as the "Windows Cloud Files Mini Filter Driver." This system driver plays a crucial role in enabling cloud applications to seamlessly integrate with and leverage file system functionalities. Adam Barnett, lead software engineer at Rapid7, a cybersecurity solutions provider, articulated the gravity of this particular flaw. He noted its significant implications, explaining that the mini filter driver is fundamental to the operation of widely used services such as OneDrive, Google Drive, and iCloud. Crucially, it remains an integral part of the Windows operating system even if none of these cloud synchronization applications are actively installed by the user, making a broad range of systems susceptible to its exploitation.

While the zero-day vulnerability is the immediate concern, Microsoft’s analysis indicates that the most critical threats in this Patch Tuesday batch are not necessarily the ones with the highest severity rating. In fact, only three of the vulnerabilities patched today were classified by Microsoft with its most severe "critical" rating. Two of these critical flaws, CVE-2025-62554 and CVE-2025-62557, are directly related to Microsoft Office. The severity of these vulnerabilities is amplified by the fact that they can be exploited simply by a user viewing a maliciously crafted email message within the email client’s Preview Pane, a common and often passive user action. A third critical vulnerability, CVE-2025-62562, affects Microsoft Outlook. However, Microsoft has specified that the Preview Pane is not an attack vector for this particular Outlook vulnerability.

Interestingly, Microsoft has flagged a different category of vulnerabilities as being most likely to be exploited from this month’s update cycle: privilege escalation bugs, even those not classified as "critical." These types of vulnerabilities are consistently a primary target for threat actors, as they allow an attacker to gain higher-level access and control over a compromised system. Microsoft’s advisory specifically calls out several of these privilege escalation vulnerabilities, including:

• CVE-2025-62458 – A flaw within the Win32k component, a core part of the Windows kernel.
• CVE-2025-62470 – A vulnerability in the Windows Common Log File System Driver, which handles logging functionalities.
• CVE-2025-62472 – A weakness in the Windows Remote Access Connection Manager, impacting remote connectivity services.
• CVE-2025-59516 and CVE-2025-59517 – Two vulnerabilities affecting the Windows Storage VSP Driver, which is involved in managing storage virtualization services.

Kev Breen, senior director of threat research at Immersive, a cybersecurity intelligence firm, provided further context on the significance of privilege escalation flaws. He stated that these types of vulnerabilities are observed in nearly every incident involving a compromise of a host system. Breen elaborated on Microsoft’s assessment, suggesting that while the specific reasons for highlighting these particular privilege escalation bugs as more likely to be exploited aren’t explicitly detailed, many of the affected components have a history of being targeted in the wild. He also pointed out that the availability of technical details from previous, similar vulnerabilities could make it easier for threat actors to develop and deploy exploits for these new flaws. Breen strongly advised that, even if not currently under active exploitation, these vulnerabilities should be patched as a matter of urgency.

Beyond the core Windows operating system and common productivity suites, this month’s Patch Tuesday also addresses a vulnerability in the rapidly evolving world of AI-powered development tools. A notable patch is for CVE-2025-64671, a remote code execution flaw affecting the GitHub Copilot Plugin for Jetbrains. This plugin, utilized by developers who rely on AI assistance for coding, is developed and maintained by Microsoft and GitHub. Kev Breen explained that this vulnerability could be exploited by tricking the large language model (LLM) powering the AI into executing commands that bypass the user’s "auto-approve" settings. This could allow an attacker to execute arbitrary code on the developer’s machine.

This specific vulnerability is part of a larger, systemic security concern that security researcher Ari Marzuk has termed "IDEsaster." This umbrella term describes a growing array of over 30 separate vulnerabilities discovered across nearly a dozen prominent AI coding platforms. These platforms include popular tools like Cursor, Windsurf, Gemini CLI, and Claude Code, indicating a widespread security challenge within the AI development tool ecosystem.

The final publicly disclosed vulnerability addressed in this December update is CVE-2025-54100, a remote code execution bug within Windows PowerShell. This vulnerability affects Windows Server 2008 and later versions. It is particularly concerning because it allows an unauthenticated attacker to execute code within the security context of the logged-in user, potentially granting them significant access and control without any prior authentication.

For IT professionals and security analysts seeking a more in-depth and granular analysis of all the security updates released by Microsoft today, the SANS Internet Storm Center provides a comprehensive roundup. As is customary with every Patch Tuesday, users and administrators are encouraged to apply these updates promptly to protect their systems from known threats. Furthermore, the community is invited to share any experiences or issues encountered while applying this month’s Windows patches in the comments section, fostering a collaborative approach to cybersecurity.