Microsoft today delivered its final Patch Tuesday of 2025, addressing a significant array of security vulnerabilities across its Windows operating systems and associated software. This month’s update cycle is particularly noteworthy as it tackles a zero-day exploit that has already been actively leveraged by malicious actors, alongside two other publicly disclosed weaknesses. In total, Microsoft has patched at least 56 security flaws, underscoring the ongoing cat-and-mouse game between software vendors and cybercriminals.

While recent months have seen a comparatively lower volume of security updates from Microsoft, 2025 has proven to be a banner year for vulnerability patching. According to Satnam Narang, a security expert at Tenable, Microsoft has addressed a staggering 1,129 vulnerabilities throughout the year, representing an 11.9% increase compared to 2024. This marks the second consecutive year and the third time in its history that Microsoft has surpassed the one-thousand-vulnerability threshold in its annual security updates, a testament to the ever-expanding threat landscape and the increasing complexity of modern software.

The most pressing issue addressed in this December update is the zero-day vulnerability, identified as CVE-2025-62221. This critical flaw is a privilege escalation bug impacting Windows 10 and subsequent versions. The weakness lies within the "Windows Cloud Files Mini Filter Driver," a fundamental system component that facilitates cloud applications’ interaction with file system functionalities. Adam Barnett, lead software engineer at Rapid7, highlighted the gravity of this discovery, stating, "This is particularly concerning, as the mini filter is integral to services like OneDrive, Google Drive, and iCloud, and remains a core Windows component, even if none of those apps were installed." This implies a broad attack surface for this specific vulnerability, regardless of user-installed cloud storage solutions.

Out of the 56 vulnerabilities patched, only three were classified by Microsoft with the highest severity rating: "critical." Two of these critical flaws, CVE-2025-62554 and CVE-2025-62557, are associated with Microsoft Office. Disturbingly, both of these can be exploited simply by a user viewing a malicious email message within the Outlook Preview Pane, a common and often subconscious user action. The third critical vulnerability, CVE-2025-62562, impacts Microsoft Outlook directly. While Microsoft has clarified that the Preview Pane is not an attack vector for this particular Outlook flaw, its critical rating still demands immediate attention from users and administrators.

Despite the "critical" designation for the Office and Outlook bugs, Microsoft’s analysis suggests that other, non-critical privilege escalation vulnerabilities are the most likely to be exploited from this month’s patch batch. These include:

• CVE-2025-62458 (Win32k): This vulnerability in the Windows kernel-mode driver is a frequent target for attackers seeking to gain elevated privileges.
• CVE-2025-62470 (Windows Common Log File System Driver): Exploiting this driver could allow an attacker to escalate their privileges.
• CVE-2025-62472 (Windows Remote Access Connection Manager): A weakness in this service could enable privilege escalation.
• CVE-2025-59516 and CVE-2025-59517 (Windows Storage VSP Driver): These two related vulnerabilities in the storage driver also present a risk of privilege escalation.

Kev Breen, senior director of threat research at Immersive, emphasized the prevalence of privilege escalation flaws in security incidents. "We don’t know why Microsoft has marked these specifically as more likely, but the majority of these components have historically been exploited in the wild or have enough technical detail on previous CVEs that it would be easier for threat actors to weaponize these," Breen commented. He further advised, "Either way, while not actively being exploited, these should be patched sooner rather than later." This sentiment highlights a proactive approach to security, urging remediation even before widespread exploitation is confirmed.

A particularly intriguing vulnerability addressed in this update is CVE-2025-64671, a remote code execution flaw affecting the GitHub Copilot Plugin for Jetbrains. This AI-powered coding assistant, widely used by developers at Microsoft and GitHub, is susceptible to attackers who could trick the large language model (LLM) into executing commands that bypass the user’s "auto-approve" settings. This vulnerability is part of a larger, more systemic issue that security researcher Ari Marzuk has termed "IDEsaster." This overarching crisis encompasses over 30 separate vulnerabilities discovered across numerous leading AI coding platforms, including Cursor, Windsurf, Gemini CLI, and Claude Code, indicating a growing area of concern for software development security.

The final publicly disclosed vulnerability patched today is CVE-2025-54100, a remote code execution bug in Windows PowerShell on Windows Server 2008 and later. This flaw is significant as it allows an unauthenticated attacker to execute code within the security context of the user, potentially leading to unauthorized access and control.

For IT professionals and security enthusiasts seeking a more detailed technical breakdown of Microsoft’s December 2025 Patch Tuesday, the SANS Internet Storm Center provides a comprehensive roundup. As is customary with any significant patch release, users are encouraged to monitor for any issues that may arise during the application of these updates and to report any problems encountered in the comments section of relevant security advisories. The consistent release of these patches is a critical defense mechanism against the ever-evolving threat landscape, and prompt application remains paramount for maintaining robust cybersecurity. The sheer volume of vulnerabilities addressed throughout 2025, coupled with the discovery of new attack vectors like those within AI coding assistants, underscores the dynamic nature of cybersecurity and the continuous need for vigilance and rapid patching.