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Q: Cisco AnyConnect VPN - Failed to initialize connection subsystem

You get an error message when trying connect to MIT's VPN using Cisco AnyConnect:

Failed to initialize connection subsystem.


  • The short answer is:

Set “vpnui.exe” to use Windows 8 compatibility mode, until Microsoft and Cisco decide who will fix the problem.

  • The longer answer is:

Microsoft recently released a Critical Security Update (KB 3023607, included as part of KB 3034682). The update changes some details of the Windows SSL/TLS API, in a way that breaks Cisco AnyConnect. Uninstalling the update would fix Cisco AnyConnect but would leave your computer vulnerable.

A Cisco support forum post recommends setting Windows 8 compatibility mode on the Cisco apps like “vpnui.exe”:
You’ll need to restart the VPN app (or the computer) after changing the compatibility settings.

As another approach, the Microsoft support page for KB 3023607 offers an “AppCompat” shim for the issue:

IS&T Contributions

Documentation and information provided by IS&T staff members

Last Modified:

February 16, 2015

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