Windows apps writing to `\\wsl.localhost` create files owned by root (UID 0) instead of WSL default user

[AntoineRoue]

Windows Version

Microsoft Windows [version 10.0.26200.8457]
(fresh install)

WSL Version

2.7.8.0
(fresh install)

Are you using WSL 1 or WSL 2?

• WSL 2
• WSL 1

Kernel Version

Linux version 6.18.33.1-microsoft-standard-WSL2

Distro Version

Ubuntu-26.04

Other Software

• Windows Explorer
• Web browsers (Chrome / Edge / Firefox downloads)

Repro Steps

1. Open Windows Explorer
2. Navigate to: \\wsl.localhost\Ubuntu-26.04\home\<user>\
3. Create a new file (Right-click → New → Text Document)
   or save a file from a browser (Chrome/Edge/Firefox) directly into this path
4. In WSL, inspect the file:

ls -ln filename

Expected Behavior

Files created from Windows via \\wsl.localhost should be owned by the WSL default user:

-rw-r--r-- 1 <user> <user> ...

(or corresponding UID/GID of default WSL user)

Actual Behavior

Files created from Windows are owned by root:

-rw-r--r-- 1 0 0 0 Jun 26 14:50 test.txt

UID/GID = 0:0

Additional observations

• WSL distro starts normally as non-root user
• Files created inside WSL (e.g. touch file) are correctly owned by non-root user

Workaround

Files copied or created from within WSL have correct ownership:

mv /mnt/c/Users/<user>/Downloads/file ~/Downloads/

Notes

I just reinstalled Windows and WSL and this behavior is new for me, I didn't do that before. This appears to be a regression in the Windows → WSL filesystem integration layer (\\wsl$ / \\wsl.localhost provider), incorrectly assigning UID 0 instead of mapping to the WSL default user.

Diagnostic Logs

I'm sorry I can't provide logs:

.\collect-wsl-logs.ps1
.\collect-wsl-logs.ps1 : Impossible de charger le fichier C:\Users<user>\collect-wsl-logs.ps1, car l’exécution
de scripts est désactivée sur ce système. Pour plus d’informations, consultez about_Execution_Policies à l’adresse
https://go.microsoft.com/fwlink/?LinkID=135170.
Au caractère Ligne:1 : 1

• .\collect-wsl-logs.ps1

•   + CategoryInfo          : Erreur de sécurité : (:) [], PSSecurityException
    + FullyQualifiedErrorId : UnauthorizedAccess
  
  

If someone is kind enough to reproduce the bug and post their logs it would be great. You'd need either a fresh Windows install, or a fresh WSL install, or a fresh Ubuntu 26.04 install, or all of the above.

[github-actions]

Logs are required for review from WSL team

If this a feature request, please reply with '/feature'. If this is a question, reply with '/question'.
Otherwise, please attach logs by following the instructions below, your issue will not be reviewed unless they are added. These logs will help us understand what is going on in your machine.

How to collect WSL logs

Download and execute collect-wsl-logs.ps1 in an administrative powershell prompt:

Invoke-WebRequest -UseBasicParsing "https://raw.githubusercontent.com/microsoft/WSL/master/diagnostics/collect-wsl-logs.ps1" -OutFile collect-wsl-logs.ps1
Set-ExecutionPolicy Bypass -Scope Process -Force
.\collect-wsl-logs.ps1

The script will output the path of the log file once done.

If this is a networking issue, please use .\collect-wsl-logs.ps1 -LogProfile networking instead, following the instructions in Collect WSL logs for networking issues

Once completed please upload the output files to this GitHub issue.

See Collect WSL logs (recommended method).

If you choose to email these logs instead of attaching them to the bug, please send them to wsl-gh-logs@microsoft.com with the GitHub issue number in the subject, and include a link to your GitHub issue comment in the message body, and reply with '/emailed-logs'.

[AntoineRoue]

I'm sorry I can't provide logs:

> .\collect-wsl-logs.ps1
.\collect-wsl-logs.ps1 : Impossible de charger le fichier C:\Users\<user>\collect-wsl-logs.ps1, car l’exécution
de scripts est désactivée sur ce système. Pour plus d’informations, consultez about_Execution_Policies à l’adresse
https://go.microsoft.com/fwlink/?LinkID=135170.
Au caractère Ligne:1 : 1
+ .\collect-wsl-logs.ps1
+ ~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : Erreur de sécurité : (:) [], PSSecurityException
    + FullyQualifiedErrorId : UnauthorizedAccess

[chemwolf6922]

Hi @AntoineRoue , The files are expected to be created as the default user. Could you please check this registry entry to see if the value is set to 0?

reg query "HKCU\Software\Microsoft\Windows\CurrentVersion\Lxss" /s /v DefaultUid

If so, please use the following command to reset the default user in registry:

wsl --manage Ubuntu-26.04 --set-default-user <user>
wsl --shutdown