Microsoft Fixes 63 Security Flaws, Including a Windows Kernel Zero-Day Under Active Attack

Microsoft has released patches for 63 new security vulnerabilities, including a Windows Kernel privilege-escalation zero-day that has been exploited in the wild, with four flaws rated Critical and 59 Important. Of the total, 29 are privilege-escalation, 16 remote code execution, 11 information disclosure, three DoS, two security‑feature bypasses and two spoofing bugs, and the update adds to the 27 Edge vulnerabilities addressed since October 2025’s Patch Tuesday.

The zero-day, CVE-2025-62215 (CVSS 7.0), was described by Microsoft as a race-condition in Windows Kernel that allows an authorised attacker to elevate privileges once they have foothold on a system, potentially enabling a SYSTEM takeover if chained with other bugs. Microsoft Threat Intelligence Center (MSTIC) and Microsoft Security Response Center (MSRC) have been credited with discovering and reporting the issue, according to Microsoft.

Additional patched flaws include two heap-based buffer overflows in Graphics Component (CVE-2025-60724, CVSS 9.8) and Windows Subsystem for Linux GUI (CVE-2025-62220, CVSS 8.8) that could lead to remote code execution, and a high‑severity privilege escalation flaw in Windows Kerberos (CVE-2025-60704, CVSS 7.5) known as CheckSum by Silverfort.

Experts warned that if exploited, the kernel race condition could enable lateral movement and credential dumping, with some noting that an initial foothold is typically required for exploitation.