Microsoft May 2025 Patch Tuesday: In-Depth Analysis of Zero-Day Vulnerabilities and Critical Flaws

On May 13, 2025, Microsoft released its monthly Patch Tuesday updates, addressing a total of 78 security vulnerabilities across its product suite. This release includes fixes for seven zero-day vulnerabilities, five of which were actively exploited in the wild prior to the update. The vulnerabilities span components such as Windows, Azure, Visual Studio, and Microsoft Defender for Identity.

Summary of May 2025 Patch Tuesday Updates

• Total Vulnerabilities Addressed: 78
• Zero-Day Vulnerabilities: 7 (5 actively exploited)
• Critical Vulnerabilities: 6
• Categories:
  • Remote Code Execution (RCE): 28
  • Elevation of Privilege (EoP): 17
  • Information Disclosure: 15
  • Denial of Service (DoS): 7
  • Security Feature Bypass: 2
  • Spoofing: 2

Detailed Examination of Zero-Day Vulnerabilities

CVE-2025-30400 – Windows Desktop Window Manager Elevation of Privilege

Severity: Important (CVSS 7.8)

A use-after-free vulnerability in the Desktop Window Manager (DWM) allows local attackers to gain SYSTEM privileges through specially crafted code.

CVE-2025-32701 – Windows CLFS Driver Elevation of Privilege

Severity: Important (CVSS 7.8)

This use-after-free vulnerability in the Common Log File System (CLFS) driver is being actively exploited and can allow local privilege escalation.

CVE-2025-32706 – Windows CLFS Driver Elevation of Privilege

Severity: Important (CVSS 7.8)

A second vulnerability in the CLFS driver, also actively exploited, that enables attackers to escalate to SYSTEM privileges.

CVE-2025-32709 – Ancillary Function Driver for WinSock Elevation of Privilege

Severity: Important (CVSS 7.8)

A local privilege escalation vulnerability through the Ancillary Function Driver for WinSock. Requires local access but was actively exploited.

CVE-2025-26685 – Microsoft Defender for Identity Spoofing

Severity: Important

Allows attackers to spoof Microsoft Defender for Identity by leveraging NTLM authentication reconfiguration. It exposes Directory Service Account credentials.

CVE-2025-32702 – Visual Studio Remote Code Execution

Severity: Important

This RCE vulnerability affects Visual Studio 2019 and 2022. Exploitation requires opening a malicious file crafted by the attacker.

CVE-2025-30385 – Windows CLFS Driver Elevation of Privilege

Severity: Important (CVSS 7.8)

Another vulnerability in the CLFS driver, similar to CVE-2025-32701/32706. While not yet exploited, Microsoft considers exploitation likely.

Other Noteworthy Vulnerabilities

CVE-2025-30405 – Microsoft Excel RCE

This flaw allows code execution if a user opens a malicious Excel file. Can lead to full user compromise.

CVE-2025-30410 – Microsoft Outlook RCE

Exploitable through crafted emails. Allows remote attackers to execute code within the user’s Outlook session.

CVE-2025-30415 – Microsoft PowerPoint RCE

Allows attackers to embed malicious code in a presentation file, triggering execution when opened.

CVE-2025-30420 – Azure DevOps Server Information Disclosure

Could expose sensitive development or operational data. Affects DevOps security workflows.

Recommendations

• Apply all updates immediately – Especially for systems exposed to the internet or handling sensitive data.
• Practice least privilege – Limit administrative access wherever possible.
• Educate users – Train them to avoid opening unexpected files or links.
• Monitor endpoints – Watch for signs of unusual activity or privilege escalation attempts.
• Update security tools – Ensure antivirus, EDR, and firewall tools are updated with the latest signatures.

Conclusion

Microsoft’s May 2025 Patch Tuesday highlights the ongoing threat landscape, with five zero-days under active exploitation. System administrators and users alike must stay vigilant and patch promptly. Maintaining good cybersecurity hygiene and staying informed is crucial for minimizing the risk of exploitation.