Microsoft Issues Security Fixes for 56 Flaws, Including Active Exploit and Two Zero-Days

Microsoft closed out 2025 with a substantial security patch release addressing 56 vulnerabilities across Windows platforms, including one actively exploited in the wild and two zero-day flaws. The December Patch Tuesday completes a year where Microsoft fixed a total of 1,275 security issues.

The critical update addresses 3 flaws rated Critical and 53 rated Important, spanning privilege escalation, remote code execution, information disclosure, denial-of-service, and spoofing vulnerabilities. Security experts highlight that this marks the second consecutive year Microsoft has patched over 1,000 CVEs.

Active Exploit Poses Significant Threat

The most concerning vulnerability, CVE-2025-62221, is already being actively exploited. This use-after-free flaw in Windows Cloud Files Mini Filter Driver allows attackers with system access to elevate privileges and obtain SYSTEM permissions.

"The Cloud Files minifilter is used by OneDrive, Google Drive, iCloud, and others, although as a core Windows component, it would still be present on a system where none of those apps were installed," explained Adam Barnett, lead software engineer at Rapid7.

Security experts warn this vulnerability could be particularly dangerous when combined with other attack methods. Mike Walters, president of Action1, noted that attackers could gain initial access through phishing or browser exploits, then use this vulnerability to take control of systems.

"Armed with this access, the attacker could deploy kernel components or abuse signed drivers to evade defenses and maintain persistence," Walters said.

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has added CVE-2025-62221 to its Known Exploited Vulnerabilities catalog, requiring federal agencies to patch by December 30, 2025.

Organizations should prioritize implementing comprehensive anti-malware security measures on all systems to detect potential exploitation attempts of this vulnerability.

Zero-Day Vulnerabilities Expose Additional Risks

Two other zero-day vulnerabilities were patched, though they're not currently known to be exploited:

• CVE-2025-54100: A command injection vulnerability in Windows PowerShell that allows unauthorized attackers to execute code locally
• CVE-2025-64671: A command injection vulnerability in GitHub Copilot for JetBrains with similar code execution capabilities

The PowerShell flaw presents significant risks according to Alex Vovk of Action1: "The threat becomes significant when this vulnerability is combined with common attack patterns. An attacker can use social engineering to persuade a user or admin to run a PowerShell snippet using Invoke-WebRequest, allowing a remote server to return crafted content that triggers the parsing flaw."

The GitHub Copilot vulnerability is part of a broader set of security issues recently dubbed "IDEsaster" by researcher Ari Marzouk. These vulnerabilities affect AI-powered development environments, including Kiro.dev, Cursor, JetBrains Junie, Gemini CLI, Windsurf, and Roo Code.

"This can be achieved through 'Cross Prompt Injection,' which is where the prompt is modified not by the user but by the LLM agents as they craft their own prompts," explained Kev Breen, senior director of cyber threat research at Immersive.

Understanding Attack Vectors

These zero-day vulnerabilities highlight how modern attackers chain multiple vulnerabilities together to compromise systems. The PowerShell vulnerability is especially concerning because PowerShell is a common administrative tool with elevated privileges on many systems. Attackers typically exploit such vulnerabilities through:

1. Phishing emails with malicious links or attachments
2. Compromised websites that deliver exploit code
3. Supply chain attacks targeting development environments
4. Social engineering tactics to trick users into executing malicious commands

Understanding these attack vectors is essential for organizations to develop appropriate mitigation strategies and implement effective methods to protect sensitive business data from unauthorized access.

Broader Industry Patching Activity

Microsoft's December update coincides with patches from numerous other technology vendors, highlighting the industry-wide effort to address security vulnerabilities:

• Adobe, AWS, AMD, Arm and ASUS released security updates
• Enterprise software makers including Atlassian, Citrix, Dell, and IBM issued patches
• Networking equipment from Cisco, F5, Fortinet and Juniper Networks received fixes
• Mobile device manufacturers Samsung, OPPO and Qualcomm addressed vulnerabilities
• Linux distributions including Red Hat, Ubuntu and Debian released security updates

The extensive patching activity comes amid heightened concerns about vulnerability exploitation, with other recent high-profile security issues including React2Shell exploits and active attacks against WinRAR vulnerability CVE-2025-6218.

Impact on Business Continuity

The scope of these vulnerabilities underscores the ongoing challenge organizations face in maintaining secure systems. For businesses, this means:

• Increased IT workload to test and deploy critical patches
• Potential service disruptions during necessary update cycles
• Additional resource allocation for vulnerability management
• Need for enhanced monitoring systems to detect exploitation attempts

This widespread vulnerability landscape demonstrates why maintaining robust cybersecurity practices is critical for modern businesses facing increasingly sophisticated threats.

How to Protect Your Systems

With the active exploitation of CVE-2025-62221 and the disclosure of two zero-day vulnerabilities, organizations should take immediate steps to protect their systems:

1. Prioritize applying Microsoft's December security patches, especially on internet-facing and critical systems
2. Update all software from third-party vendors, as many released concurrent security patches
3. Implement additional security controls like network segmentation and endpoint protection
4. Monitor systems for signs of compromise, particularly around file system activity

These vulnerabilities highlight the ongoing importance of timely patching and defense-in-depth strategies to protect against increasingly sophisticated cyber threats. Organizations should also consider security awareness training to reduce the risk of social engineering attacks that could exploit these vulnerabilities.

Creating an Effective Vulnerability Management Process

To better address these types of security issues, organizations should establish a formalized vulnerability management process that includes:

• Regular vulnerability scanning of all systems and applications
• Risk-based prioritization of vulnerabilities based on threat intelligence
• Clear patch management procedures with defined timelines for critical vs. non-critical updates
• Documented exception processes when patches cannot be immediately applied
• Compensating controls for systems that cannot be patched quickly

The security updates serve as a reminder that even as the year ends, cybersecurity vigilance remains essential to protect critical systems and data from exploitation.