Microsoft Patch Tuesday, September 2026 Security Update Review
Microsoft's September 2026 Patch Tuesday fixes 974 vulnerabilities, including 113 critical and two actively exploited Windows privilege escalation flaws.
Microsoft's September 2026 Patch Tuesday fixes 974 vulnerabilities, its largest release ever, including 113 critical and 860 important, covering Windows HTTP.sys, Hyper-V, Entra ID, Exchange Server, Office, DNS, and more. Two zero-days are confirmed exploited in the wild: CVE-2026-81963 (Windows Update Stack EoP) and CVE-2026-85880 (ALPC heap overflow), both letting authenticated attackers gain SYSTEM privileges. Notable criticals include an Entra ID authentication bypass (CVE-2026-62916) and multiple Windows DNS Server and Office remote code execution flaws.
Microsoft Releases Emergency Windows 11 Update Following Patch Tuesday Bugs
Microsoft issued emergency Windows 11 update KB5129195 to fix Patch Tuesday regressions and fully close the CVE-2026-62721 privilege escalation flaw.
Microsoft shipped out-of-band cumulative update KB5129195 for Windows 11 24H2 and 25H2 (builds 26100.9457 and 26200.9457) after the September 8 Patch Tuesday rollup, which addressed over 960 CVEs including two actively exploited flaws, broke Remote Desktop Services, Hyper-V Plan9 folder sharing, and USB audio. The emergency release also strengthens the incomplete fix for CVE-2026-62721, an elevation-of-privilege flaw in the Windows User-Mode Power Service that could let a local attacker gain SYSTEM privileges. Companion patches cover Windows 11 26H1, Windows 10, and Windows Server. Some USB Audio Class 1.0 and AMD Radeon graphics issues remain unresolved.
Windows 11 Security Update KB5124008 Breaks Always-On VPN Connections
Microsoft's September 2026 Windows 11 update KB5124008 breaks certificate-based Always On VPN on some enterprise clients, forcing admins to pause rollout.
Microsoft's September 8, 2026 cumulative update KB5124008 for Windows 11 24H2 (build 26100.9445) and 25H2 (build 26200.9445) breaks certificate-based Always On VPN tunnels on some enterprise clients, with connectivity restored after uninstalling the update and rebooting. The issue was first detailed on Microsoft Q&A on September 9 by an administrator using Intune-deployed VPN profiles with RRAS and NPS on Windows Server 2019. The same mandatory Patch Tuesday package fixes two actively exploited zero-days, CVE-2026-81963 in the Windows Update Stack and CVE-2026-85880 in Windows Advanced Local Procedure Call, so many teams are pausing only VPN cohorts rather than blocking the full rollout.
Microsoft Plugs Nearly 1,000 Security Holes
Microsoft's September Patch Tuesday fixes a record 974 flaws, including two actively exploited Windows zero-days and critical DNS and Windows Shell bugs.
Microsoft released fixes for 974 vulnerabilities, its largest-ever monthly patch batch, bringing the 2026 total above 2,600. Two zero-day privilege elevation flaws, CVE-2026-81963 and CVE-2026-85880, are being actively exploited. Critical bugs include CVE-2026-69730, an unauthenticated DNS weakness in Windows Server 2012 onward and Windows 10 deemed likely to be exploited, and CVE-2026-69829, a CVSS 9.8 Windows Shell remote code execution flaw requiring no privileges or user interaction. Microsoft and other vendors credit AI-assisted discovery for the growing patch volumes.