Microsoft has issued fixes for three zero-day vulnerabilities in its first Patch Tuesday release of 2026, including one flaw the company says was being actively exploited before patches were available, according to reporting from Infosecurity Magazine.
The company’s January security update was described as a busy release, with the zero-days standing out because they were known to attackers or defenders before remediation. At least one of the vulnerabilities had already been used in real-world attacks, which raises the priority for enterprise patching teams and incident responders. Microsoft had not, at the time of the report, publicly provided all of the technical detail needed to assess how broadly the bugs were being abused or whether they were tied to a named threat actor campaign.
Zero-days in Microsoft’s monthly updates often involve elevation-of-privilege, remote code execution or security feature bypass issues. In practice, those flaws are frequently chained with phishing, malware delivery or stolen credentials to deepen an intrusion after initial access. That means defenders should treat this month’s updates as more than routine maintenance, especially for internet-facing systems, high-value endpoints and Windows servers.
The immediate task for organizations is to identify exposed assets, apply the relevant updates, and review logs for signs of exploitation that may have occurred before patching. Security teams should also watch for follow-on activity after disclosure, as attackers commonly reverse-engineer fixes and build new exploits once patch details become public. Remote staff and unmanaged devices may need extra attention, particularly if they sit outside normal update cycles or connect over public networks without a VPN.
Because the initial report does not include the full CVE list or Microsoft advisory detail, defenders should verify the affected products, exploitation status and severity ratings directly in Microsoft’s Security Response Center and Update Guide before setting patching priorities. If CISA adds any of the flaws to its Known Exploited Vulnerabilities catalog, US federal agencies and many private-sector teams will likely face tighter remediation deadlines.
For now, the main takeaway is straightforward: this month’s Microsoft updates include three zero-days, one already exploited, making rapid validation and deployment a priority for Windows administrators.
