Microsoft has acknowledged that recent security updates for Windows 11 are leading to networking complications for enterprise users utilizing the Windows Subsystem for Linux (WSL). This issue primarily affects those who have installed the KB5067036 non-security update from October 28, 2025, or any subsequent updates, including the KB5072033 cumulative update released during this month’s Patch Tuesday.
Connectivity Challenges for VPN Users
Users encountering this problem are experiencing difficulties with certain third-party VPN applications when the mirrored mode networking feature is enabled. This disruption hinders access to essential corporate resources. Mirrored mode networking, which was introduced in WSL back in September 2018, was designed to enhance VPN compatibility, support IPv6 and multicast, and facilitate connections to WSL from local area networks (LAN) as well as from Windows servers to Linux environments.
The connectivity issues manifest as “No route to host” errors within WSL environments, despite the fact that the Windows host systems can typically reach the same destinations without difficulty. The problem notably impacts OpenVPN and enterprise VPN solutions, including Cisco Secure Client, formerly known as Cisco AnyConnect.
The root of the issue lies in the failure of VPN applications’ virtual network interfaces to respond to Address Resolution Protocol (ARP) requests, which are crucial for mapping IP addresses to MAC (Media Access Control) addresses. Microsoft explained, “This issue happens because the VPN application’s virtual interface doesn’t respond to ARP requests.” It is worth noting that home users operating Windows Home or Pro editions are unlikely to be affected, as the issue predominantly disrupts connectivity to enterprise resources over VPN, including DirectAccess.
As of now, Microsoft is actively investigating the matter but has not yet provided a timeline for a resolution or any potential workarounds. The company has assured users that further information will be shared as it becomes available.
WSL itself was launched in March 2018 as a compatibility layer, allowing users to run Linux distributions natively on their Windows machines through PowerShell or the Windows 10 command prompt. A significant upgrade, WSL 2, was introduced in May 2019, featuring a real Linux kernel operating within a virtual machine, along with notable enhancements in file-system performance and comprehensive system-call compatibility.
In a move towards greater transparency and collaboration, Microsoft open-sourced WSL at Microsoft Build 2025, making its source code accessible on GitHub, with the exception of a few components that remain part of Windows.
