Patch Tuesday 2025 roundup: The biggest Microsoft vulnerabilities of the year
Tuesday, December 30, 2025
What
Microsoft's 2025 Patch Tuesday presented a significant challenge, with 1,246 CVEs, 158 rated critical, and 41 identified as zero-days. Security professionals flagged specific vulnerabilities as most concerning, including critical remote code execution and privilege escalation flaws across Windows, SharePoint, and Active Directory. The urgency for patching has intensified due to threat actors leveraging AI and new tactics to exploit vulnerabilities almost immediately after Patch Tuesday, leaving organizations with less time to implement defenses.
Where
The vulnerabilities primarily affect Microsoft systems, including Windows operating systems, SharePoint 2016/2019 servers, Microsoft Office, Active Directory environments, and the Microsoft Management Console (MMC). These systems are widely used by organizations globally.
When
The vulnerabilities were disclosed as part of Microsoft's Patch Tuesday in 2025, which typically occurs on the second Tuesday of each month. Some specific vulnerabilities, like CVE-2025-30377, were revealed in May of that year, with active exploitation occurring shortly after disclosure.
Key Factors
- •The ToolShell (CVE-2025-53770) vulnerability, a chained remote code execution flaw in on-premises SharePoint 2016/2019 servers with a CVSS score of 9.8, was actively exploited by initial access brokers, posing a 'nightmare scenario' for affected organizations.
- •The Kerberos BadSuccessor (CVE-2025-53779) privilege escalation vulnerability allowed any domain-authenticated account to escalate privileges by spoofing tokens within Active Directory environments, providing an 'express elevator to domain admin' for ransomware operators.
- •Several zero-day vulnerabilities, including CVE-2025-26633 (MMC security feature bypass) and CVE-2025-33053 (Internet Shortcut Files RCE), were actively abused by threat actors like the APT Stealth Falcon to deploy malware such as the MSC EvilTwin trojan loader and Horus Agent.
- •Vulnerabilities affecting Preview Pane attacks in Windows and Office, such as CVE-2025-30377, allowed for silent remote code execution when an employee simply previewed a specially crafted file or email, representing a significant and often overlooked risk.
Takeaways
- →Organizations must prioritize patching based on the actual risk and exploitability of vulnerabilities, rather than solely relying on CVSS scores, and automate the deployment of critical updates to reduce exposure time.
- →The accelerated pace of threat actor exploitation, driven by AI and new tactics, necessitates a shift from traditional 30-day or quarterly patching cycles to much faster, risk-based patching strategies.
- →Defend against 'silent exploits' like Preview Pane attacks by configuring systems to disable or restrict preview functionality for untrusted sources, and rigorously patch privilege escalation flaws that can lead to rapid domain compromise or ransomware deployment.
Opens original article on CSO Online
