WSL with networkingMode=mirrored does not refuse localhost connection while the port is not open

[KaneGreen]

Windows Version

Microsoft Windows [Version 10.0.26100.2033]

WSL Version

2.3.24.0

Are you using WSL 1 or WSL 2?

• WSL 2
• WSL 1

Kernel Version

5.15.153.1

Distro Version

Ubuntu 24.04.1 LTS

Other Software

No response

Repro Steps

1. %USERPROFILE%.wslconfig

[wsl2]
networkingMode=mirrored

2. Use any tool to connect to an unopened port on 127.0.0.1
   For example:
   (assuming no program is using or listening on port 1234)

curl -v http://127.0.0.1:1234/

(if you tried non-local adress, for example, curl -v http://www.bing.com:1234/, the connection failed quickly, which is expected )

Expected Behavior

Connection refused

Actual Behavior

Connection persists, no data is received

Diagnostic Logs

I don't think it's necessary

[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-networking-logs.ps1, following the instructions here

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

Click here for more info on logging
If you choose to email these logs instead of attaching to the bug, please send them to wsl-gh-logs@microsoft.com with the number of the github issue in the subject, and in the message a link to your comment in the github issue and reply with '/emailed-logs'.

View similar issues

Please view the issues below to see if they solve your problem, and if the issue describes your problem please consider closing this one and thumbs upping the other issue to help us prioritize it!

Open similar issues:

• Mirrored networking does not loopback the entire 127.0.0.0/8 range (#11766), similarity score: 0.77
• Windows programs unable to communicate on localhost, maybe due to mirrored mode wsl bug. (#11417), similarity score: 0.77

Closed similar issues:

• Mirrored networking mode makes requests to localhost:PORT wait 2 minutes (#10844), similarity score: 0.82
• WSL 2.0.6 mirrored network - can not connect to Docker container ports from Windows host (#10683), similarity score: 0.78
• WSL 2.0: networkingMode=mirrored makes Docker unable to forward ports (#10494), similarity score: 0.77

Note: You can give me feedback by thumbs upping or thumbs downing this comment.

[KaneGreen]

similar to #10855