Microsoft’s October 2025 Patch Tuesday: Largest Release and Exploited Zero-Days
Microsoft has issued its largest Patch Tuesday security update to date in October 2025, addressing 167 distinct Common Vulnerabilities and Exposures (CVEs), including three zero-day vulnerabilities. Of particular note, two of these zero-days were actively exploited in the wild prior to the release of patches. The scope and technical details of this release highlight evolving threat models affecting modern Windows systems, as well as the company’s sustained efforts to mitigate privilege escalation and exploitation risks associated with core Windows functionality.
Scale and Severity of Patch Tuesday
The October 2025 update contains patches for 167 CVEs, making it the largest security release from Microsoft yet. Within this release, seven vulnerabilities have been rated as critical, 158 as important, and two as moderate in their severity. Notably, the vulnerability tracking did not account for 27 additional CVEs, which were specific to Chromium, MITRE, GitHub, CERT/CC, and distinct cloud advisories published separately earlier in the month.
Zero-Day Vulnerabilities
Among the addressed vulnerabilities, three were classified as zero-day, with two confirmed as exploited in the wild. Zero-day vulnerabilities represent flaws that are exploited before the vendor is aware and can release a remediation, making their timely detection and patching vital. Technical deep-dives into these vulnerabilities indicate that successful exploitation often allows attackers to gain elevated system privileges, bypass security boundaries, or execute code with SYSTEM-level access. Details on specific CVE identifiers and their exploitation mechanisms have been made available for operational security teams to respond proactively.
CVE-2025-55680: Windows Cloud Files Mini Filter Driver
CVE-2025-55680, a privilege escalation vulnerability within the Windows Cloud Files Mini Filter Driver, is specifically noted from this release. It carries a CVSSv3 score of 7.8 and is assessed as “Exploitation More Likely.” Exploitation requires a local, authenticated attacker to trigger and win a race condition, enabling the elevation to SYSTEM privileges. The cloud files driver has historically surfaced repeated vulnerabilities, with a total of 17 vulnerabilities since 2022 and several patched as active zero-days. This persistent attack surface underscores the importance of monitoring file system drivers for race conditions and privilege escalation vectors in enterprise Windows deployments.
Granular Breakdown of Patches
Microsoft’s update includes remediation for a broad spectrum of exploited and theoretical attack points, encompassing kernel drivers, user-mode components, remote code execution flaws, and authentication bypasses. Security teams are advised to prioritize patches for critical and widely exploited vulnerabilities, and to review advisory documentation for potential signs of compromise.
Windows 10 End of Support: Security Implications
Coinciding with the October 2025 update is the formal end of support for Windows 10. Systems running Windows 10 will cease to receive standard security updates and are now only eligible for continued coverage under the Extended Security Updates (ESU) program. Specific plugin identifiers have been published to help IT staff pinpoint unsupported versions, especially those deployed under long-term servicing branches (LTSB) for both Enterprise and IoT editions, which also reached end-of-support on October 14, 2025.
Recommendations for Security Teams
Immediate patching is essential for high and critical vulnerabilities, especially those with known exploits in the wild. Organizational asset managers should inventory and assess Windows 10 deployments and onboard unsupported endpoints to ESU or migrate to newer operating systems. Security monitoring should be configured to detect exploitation attempts targeting cloud file drivers and system privilege escalation vectors. Proactive review of released advisories, combined with defense-in-depth strategies, can mitigate risks while sustaining compliance and resilience against emerging attack campaigns.