Microsoft has issued security updates for 120 flaws, including 12 vulnerabilities rated as "Critical," as part of the Patch Tuesday updates for May 2026. This month is notable for having no documented zero-day vulnerabilities, a rare reprieve that allows IT teams to focus on a massive wave of Remote Code Execution (RCE) and Elevation of Privilege fixes across the Windows ecosystem.
Zero-Days Fixed
For the first time in several cycles, Microsoft has reported that no vulnerabilities were being actively exploited or publicly disclosed prior to the release of these patches. While there are no "fires to put out" today, the high count of RCE flaws, many of which are "wormable", means that the race between patch deployment and AI-generated exploit discovery remains the primary concern for 2026.
Critical Vulnerabilities to Prioritise
Of the 120 flaws, twelve received a "Critical" rating. These require immediate attention, particularly those affecting network services and office productivity tools,
- CVE-2026-42897 - Windows Network File System (NFS) Remote Code Execution
Impact - This is the most significant flaw of the month with a CVSS score of 9.8. It allows an unauthenticated attacker to execute code at the system level by sending a specially crafted call to an NFS service. This is a high-priority fix for any organization using Windows-based storage for Linux interoperability or mixed-OS environments.
- CVE-2026-41093 - Microsoft Word Critical RCE
Impact - This vulnerability allows for code execution via the Outlook Preview Pane. Because a user does not even need to open the document to be compromised, this serves as a primary vector for initial access in phishing campaigns.
- CVE-2026-40854 - Windows Kerberos Elevation of Privilege
Impact - A critical vulnerability in the core Windows authentication protocol. If exploited, an attacker with a low-privilege foothold can elevate their status to Domain Administrator, effectively gaining full control over the identity infrastructure.
- CVE-2026-41101 - Windows Routing and Remote Access Service (RRAS) RCE
Impact - An unauthenticated attacker could send crafted packets to a server running the RRAS service to achieve remote code execution, making this a critical concern for remote-work infrastructure.
Vulnerabilities by Category
The May 2026 updates addressed a total of 120 flaws, categorised as follows:
- Elevation of Privilege Vulnerabilities - 58
- Remote Code Execution Vulnerabilities - 23
- Information Disclosure Vulnerabilities - 20
- Spoofing Vulnerabilities - 9
- Denial of Service Vulnerabilities - 4
- Security Feature Bypass Vulnerabilities - 3
- Tampering Vulnerabilities - 3
- Total Flaws - 120
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Originally published on LinkedIn.