Always On VPN fails after installing KB5124008 on Windows 11

Tifoso1979 10 Reputation points
2026-09-09T08:45:16.16+00:00

Hello,

We are experiencing an issue with Always On VPN after installing the September 2026 Windows 11 security update KB5124008.

Environment

  • Windows 11 clients (24H2/25H2)
  • Always On VPN
  • Certificate-based authentication
  • RRAS + NPS on Windows Server 2019
  • Microsoft Intune deployed VPN profile

Issue

After installing KB5124008, Always On VPN stops working.

Troubleshooting performed

We have been able to reproduce the issue consistently:

  1. Always On VPN works normally before installing KB5124008.
  2. Install KB5124008.
  3. Always On VPN no longer connects/functions correctly.
  4. Uninstall KB5124008.
  5. Reboot the device.
  6. Always On VPN works again immediately.

The behavior has been reproduced on multiple client devices.Hello,

We are experiencing an issue with Always On VPN after installing the September 2026 Windows 11 security update KB5124008.

Environment

  • Windows 11 clients (24H2/25H2)
  • Always On VPN
  • Certificate-based authentication
  • RRAS + NPS on Windows Server 2019
  • Microsoft Intune deployed VPN profile

Issue

After installing KB5124008, Always On VPN stops working.

Troubleshooting performed

We have been able to reproduce the issue consistently:

  1. Always On VPN works normally before installing KB5124008.
  2. Install KB5124008.
  3. Always On VPN no longer connects/functions correctly.
  4. Uninstall KB5124008.
  5. Reboot the device.
  6. Always On VPN works again immediately.

The behavior has been reproduced on multiple client devices.

We stopped to rollout KB5124008

Windows for business | Windows Client for IT Pros | Networking | Network connectivity and file sharing

9 answers

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  1. Mitchel 0 Reputation points
    2026-10-14T14:59:04.1566667+00:00

    We’re experiencing the same issue. Yesterday, Microsoft finally released KB5127648, which was supposed to include the fix for the Always On VPN issue. Unfortunately, the issue still persists in our environment.

    We’ve tried wiping the device and removing the VPN profile, but neither has resolved the problem. Even fully updating the device to KB5127648 first and only then deploying the VPN configuration doesn’t resolve the issue.

    The only workaround that works is completely uninstalling the update, just as we’ve had to do with every update released since KB5124008.

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    2 people found this answer helpful.
  2. NKT 0 Reputation points
    2026-10-14T07:51:38.45+00:00

    October 13, 2026—KB5127648 (OS Builds 26300.9711, 26200.9711 and 26100.9711)

    • [Always On VPN] This update fixes an issue that affects Always On VPN connections after installing KB5124008. When automatic protocol selection or protocol fallback was configured, affected VPN connections could remain stuck in a Connecting state or fail to connect after an initial connection attempt failed. In some cases, subsequent connection attempts could display the error, "The specified port is already in use."

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    1 person found this answer helpful.
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  3. Jaap Hiemstra | Jaap Solutions 0 Reputation points
    2026-09-23T15:37:03.6633333+00:00

    We have the same issue with a lot of laptops, also mine. What I found out

    I can connect to the AOVPN using my phone as a hotspot which has an IP V6 address.

    I cannot connect to the AOVPN using my normal internet connection witch uses an IP V4 address.

    When I am connected with the use of the hotspot and then switch over to my normal internet connection, the VPN stays connected.

    Weird right?

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  4. Tifoso1979 10 Reputation points
    2026-09-16T06:49:37.6766667+00:00

    I couldn't find VPN bug fixings in the release notes of KB5129195. any official information from MS?

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