Virtualization New Added 26 October 2026

wsl: A localhost proxy configuration was detected but not mirrored into WSL

Windows has a proxy set at 127.0.0.1 or localhost, usually from a corporate VPN client, Fiddler or a tool such as Clash, and WSL 2 tried to copy it into Linux as HTTP_PROXY. In the default NAT networking mode, localhost inside WSL is the Linux VM rather than Windows, so that address would lead nowhere and WSL drops it. Linux tools then go direct and fail on networks that require the proxy, while the same command works fine in PowerShell.

Quick fix

Read the commands before running them. Anything that restarts a service, deletes data or changes permissions should be tried on a non-production system first.

Quick fix

# On Windows: what proxy is configured?
netsh winhttp show proxy
Get-ItemProperty 'HKCU:\Software\Microsoft\Windows\CurrentVersion\Internet Settings' | Select-Object ProxyEnable, ProxyServer, AutoConfigURL

# Fix 1 (Windows 11 22H2+): mirrored networking shares localhost with Windows
# %UserProfile%\.wslconfig
# [wsl2]
# networkingMode=mirrored
# autoProxy=true
wsl --shutdown

# Fix 2, staying on NAT: point Linux at the Windows host instead of localhost.
# The proxy must listen on that interface, not only on 127.0.0.1
export https_proxy="http://$(ip route show default | awk '{print $3}'):8080"

# Check from inside WSL
env | grep -i _proxy

How to diagnose Virtualization errors

Virtualisation errors are usually about hardware virtualisation access: either it is disabled in firmware, or another hypervisor already holds it. On Windows, Hyper-V, WSL 2, Docker Desktop, Credential Guard and memory integrity all claim the virtualisation extensions, and VirtualBox or VMware then fails with a message that mentions VT-x but not the actual conflict.

If the quick fix above does not resolve it, work through these steps. They apply to this whole class of error, not just to this one message, which is usually what saves the time.

Confirm virtualisation is enabled at the CPU level: grep -E 'vmx|svm' /proc/cpuinfo on Linux, or the Performance tab of Task Manager on Windows.
On Windows, check what else is using the hypervisor: bcdedit /enum | findstr hypervisorlaunchtype and whether Hyper-V, WSL 2 or Core Isolation are enabled.
On Linux, check /dev/kvm exists and that your user is in the kvm group; nested virtualisation must be enabled explicitly on cloud VMs.
Match guest additions and tools versions to the hypervisor version: mismatches cause shared folders, clipboard and display problems that look like guest OS bugs.
For WSL, run wsl --status and wsl --update; most WSL 2 errors are a stale kernel or a disabled Virtual Machine Platform feature.

Tools worth reaching for

grep -E 'vmx|svm' /proc/cpuinfo
wsl --status
bcdedit /enum
ls -l /dev/kvm
systemctl status libvirtd

Authoritative references

Primary documentation for this error, worth reading before applying any fix in production.

learn.microsoft.com learn.microsoft.com

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