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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.

Cyber Security Newsupdated · 1d agofirst · 5d agoVulnerability in the wild 23 sourcesCVE-2026-81963CVE-2026-858801

Windows 11 cumulative updates KB5124008 & KB5122880 released

Microsoft shipped mandatory September 2026 Patch Tuesday cumulative updates KB5124008 and KB5122880 for Windows 11, fixing vulnerabilities and adding features.

Microsoft released Windows 11 KB5124008 (versions 25H2/24H2) and KB5122880 (23H2) cumulative updates containing the September 2026 Patch Tuesday security patches, described as covering 1,000 vulnerabilities discovered in previous months. The updates are mandatory and add features including movable and resizable taskbars, Start menu customization, a Windows Search option to hide Bing and Store web suggestions, and Administrator Protection, a just-in-time admin privilege feature that is off by default and configurable via Intune OMA-URI or Group Policy.

BleepingComputer · 7d agoAdvisory

Microsoft Confirms Remote Desktop Services Might Stop Working Following Sept. 2026 Security Update

Microsoft's September 2026 Patch Tuesday updates (KB5124008) can break Remote Desktop Services, causing RDP failures and freezes across Windows clients and servers.

Microsoft confirmed its September 2026 security updates, including KB5124008 for Windows 11 24H2/25H2, introduced a reliability regression where RDP connections fail after several minutes and servers hang at the 'Please wait for the Remote Desktop Configuration' screen. MMC, RDS Licensing Diagnoser, File Explorer, and the Windows Update settings page may also stop responding. The issue affects Windows 10/11 clients and Windows Server 2012 through 2025; Microsoft marked it Mitigated on September 11 and is developing a permanent fix, with VM restart offered as a temporary workaround.

Cyber Security News · 2d agoAdvisory

Microsoft: September updates cause RDS failures on Windows Server

Microsoft confirms September 2026 Patch Tuesday updates break Remote Desktop Services on Windows Server 2012+; Group Policy mitigations and rollback workarounds available.

Microsoft confirmed that September 2026 Patch Tuesday security updates cause Remote Desktop Services failures on Windows Server 2012 and later, plus Windows 10 and Windows 11. Symptoms include unstable RDS, RDP connection failures after several minutes, sign-in issues, servers hanging at 'Please wait for the Remote Desktop Configuration,' and unresponsive MMC, RDS Licensing Diagnoser, and File Explorer. Microsoft published per-version Group Policy mitigations (covering KBs such as KB5124008, KB5122880, KB5122878, KB5122871, KB5122882, KB5122876, KB5123099, KB5123065, KB5123066) and suggests restarting affected VMs. Rolling back the updates restores RDS functionality but removes this month's security fixes.

BleepingComputerupdated · 1d agofirst · 2d agoAdvisory 3 sources1