In a major security update, Microsoft has released fixes for a total of 161 security vulnerabilities in Windows and related software, including three zero-day vulnerabilities that are currently being exploited by attackers. This release marks the largest number of fixes shipped by Microsoft in a single update since 2017.
According to Rapid7’s Adam Barnett, Microsoft has been consistently publishing zero-day vulnerabilities on Patch Tuesday for the past four months without initially classifying them as critical severity. Additionally, the latest update includes nine critical remote code execution (RCE) vulnerabilities.
The zero-day vulnerabilities that are already being actively exploited are identified as CVE-2025-21333, CVE-2025-21334, and CVE-2025-21335. These vulnerabilities are found in Windows Hyper-V, a critical component of modern Windows 11 operating systems used for security features like device guard and credential guard.
Security researchers have pointed out that these vulnerabilities are related to privilege escalation, which allows attackers to gain higher privileges on a compromised system. Elevation of privilege bugs, like the ones mentioned in this update, are often used by attackers after accessing a target system to gain further access and control.
Some of the vulnerabilities addressed in this update have been rated with high CVSS scores, including CVE-2025-21298, which allows attackers to execute arbitrary code through a malicious .rtf file. Another critical vulnerability, CVE-2025-21311, affects the Windows NTLMv1 authentication protocol, making it remotely exploitable by attackers with minimal skills.
One particularly noteworthy fix is CVE-2025-21210, which addresses a vulnerability in Microsoft’s Bitlocker full disk encryption suite. This bug could potentially expose sensitive data stored in hibernation images, which are created when a laptop goes to sleep and contain data from the device’s RAM.
Furthermore, Microsoft has patched a series of vulnerabilities in Microsoft Access, identified by Unpatched.ai, a security research project utilizing artificial intelligence to discover vulnerabilities in code. These remote code execution bugs can be exploited through social engineering attacks where a malicious file is downloaded and executed by the target.
For Windows users, it is strongly recommended to install these updates to protect against potential security threats. It is advisable to back up important files before updating and to reach out for assistance if encountering any issues during the installation process.
For more information on the latest Microsoft patches, readers can refer to resources such as the Tenable blog, SANS Internet Storm Center, and Ask Woody. Stay informed and stay safe online.