Microsoft WSUS Sync Bug Leaves Critical Patches Undeployed

On July 21, 2026, Microsoft released manual remediation guidance for Windows Server Update Services (WSUS) administrators facing synchronization issues. The problem, which began on July 13, 2026, has prevented the deployment of critical patches for two actively exploited zero-day vulnerabilities, CVE-2026-56164 and CVE-2026-56155, released on July 14. These vulnerabilities affect on-premises SharePoint Server and Active Directory Federation Services, respectively. The WSUS outage is the fourth in fourteen months and highlights structural risks in Microsoft's deprecated WSUS product. The vulnerabilities are categorized as critical by the National Vulnerability Database, with one having a CVSS score of 9.8. The urgency is compounded by a federal remediation deadline that has already passed, leaving many organizations vulnerable.

Key Points: • Microsoft issued a manual fix for WSUS sync issues affecting critical patch deployment. • Two zero-day vulnerabilities, CVE-2026-56164 and CVE-2026-56155, are actively exploited. • The WSUS outage is the fourth in fourteen months, raising concerns about its reliability.