Microsoft says that recent Windows 11 security updates are causing VPN networking failures for enterprise users running Windows Subsystem for Linux.
This known issue affects users who installed the KB5067036 October 2025 non-security update, released October 28th, or any subsequent updates, including the KB5072033 cumulative update released during this month’s Patch Tuesday.
On impacted systems, users are experiencing connectivity issues with some third-party VPN applications when mirrored mode networking is enabled, preventing access to corporate resources.
Mirrored mode networking was introduced in WSL in September 2018 to improve VPN compatibility, add IPv6 and multicast support, and enable connecting to WSL from the local area network (LAN) and to Windows servers from within Linux.
Those affected by this bug are seeing “No route to host” errors in WSL environments, even though their Windows host systems can normally access the same destinations. According to Microsoft, the problem affects OpenVPN and enterprise VPN solutions, such as Cisco Secure Client (formerly Cisco AnyConnect).
The issue stems from VPN applications’ virtual network interfaces failing to respond to Address Resolution Protocol (ARP) requests, which map IP addresses to MAC (Media Access Control) addresses.
“This issue happens because the VPN application’s virtual interface doesn’t respond to ARP (Address Resolution Protocol) requests,” Microsoft said. “Home users of Windows Home or Pro editions are unlikely to experience this issue. It primarily affects connectivity to enterprise resources over VPN, including DirectAccess.”
Microsoft says it’s investigating this known issue but has yet to provide a timeline for a fix or a workaround, and added that additional information would be shared when available.
WSL was introduced in March 2018 as a compatibility layer that enables users to run Linux distributions natively on their Windows computers via PowerShell or the Windows 10 command prompt.
In May 2019, Microsoft released WSL 2, a major upgrade including a real Linux kernel running in a virtual machine, notable improvements in file-system performance, and extended support for complete system-call compatibility.
Microsoft open-sourced WSL at Microsoft Build 2025, making its source code available on GitHub, except for a handful of components that are part of Windows.
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