Microsoft Windows 11 updates break VPN and Remote Desktop

September 2026 Windows 11 updates broke Always On VPN, now fixed, and can still break non-admin Remote Desktop.

Microsoft confirmed two separate Windows 11 issues tied to September 2026 updates. Non-admin users can fail to connect over Remote Desktop after installing the KB5124010 preview or later updates when Administrator protection is enabled, returning error 0xC000000D on Windows 11 24H2, 25H2, 26H1, and 26H2. The feature is enabled by default in the relevant Windows security baselines, and until a fix ships administrators can disable it through Intune or Group Policy. Separately, September 2026 security updates broke Always On VPN on Windows 11 24H2 and later when automatic selection or fallback between IKEv2 and SSTP left connections stuck in Connecting or reporting that the specified port was already in use. October cumulative updates KB5127648 and KB5127646 resolve the VPN failure; administrators who cannot patch immediately can force SSTP-only or IKEv2-only profiles. The sources do not disagree; the later report adds the VPN fix and only briefly notes the Remote Desktop problem.

• Microsoft says non-admin Remote Desktop connections can fail with error 0xC000000D after the September 2026 KB5124010 preview or later updates when Administrator protection is enabled.
• Affected Remote Desktop systems include Windows 11 24H2, 25H2, 26H1, and 26H2; Administrator protection is on by default in the relevant Windows security baselines.
• Until a Remote Desktop fix ships, administrators can disable Administrator protection through Intune or Group Policy.
• September 2026 Windows 11 security updates broke Always On VPN automatic selection or fallback between IKEv2 and SSTP on Windows 11 24H2 and later.
• Affected VPN connections could stay in Connecting or return “The specified port is already in use.”
• Cumulative updates KB5127648 and KB5127646 fix the Always On VPN issue; a temporary workaround is forcing SSTP-only or IKEv2-only profiles.
• Microsoft previously fixed similar Remote Desktop failures in 2025 and September 2026.
• Both reports are dated 2026-10-14; the later report notes the Remote Desktop problem separately from the VPN fix.