Issue Anonymous FTP 500 Type Error

[cobanramo]

Server operating system version

VPS Server Ubuntu 24.04.1 LTS

Plesk version and microupdate number

Plesk Obsidian v18.0.66_build1800250106.19 os_Ubuntu 24.04

Hi guys,
When I click on the Anonymous FTP it triggers a 500 Type Error, is this a configuration problem or a bug, can someone help me out?
My configuration is only FTPS and I can connect normally using WinScp and user data.
I've already checked everything with Diagnosis & Repair, but I just can't get any further.

Regards Coban

 

[Sebahat.hadzhi]

I am unable to replicate the issue on a Ubuntu 24.04 server. Have you tried the repair option, please?

 

[cobanramo]

Hello Sebahat,

Of course, first I ran the diagnosis & repair, then later the RepairKit in this error message.
The Plesk installation repair didn't help either.
As soon as this error occurs, there are also a lot of error messages in the log. But there is no malfunction, I don't know what it's all about.
I noticed this problem when I created an FTP user a few days ago, I didn't get around to it before.

Regards R.Sivgin

 

[UHolthausen]

Hello

same problem with debian 12.9 an Plesk Obsidian 18.0.67. Web Pro Edition
Plesk repair doesnt show any problems.

 

[Sebahat.hadzhi]

Could any of you open a support ticket for further investigation, please? The Anonymous FTP is working fine on Ubuntu/Debian when I test it, however, since both of you are experiencing the same issue and you are both on Debian-based systems there might indeed be some sort of compatibility issue. Unfortunately, without investigation it is quite difficult to determine the exact reason for it.

 

[cobanramo]

I've created a ticket, let's see what comes out of it.

Greetings

 

[cobanramo]

So guys,

I had great support from the Plesk team today,
The problem appears to have been temporarily fixed with a patch.
I was informed that the Plesk Development team is aware of the issue and actively working on a permanent fix.
For more details and updates, users can always check the official Plesk changelog here: https://docs.plesk.com/release-notes/obsidian/change-log/

The issue was caused by incorrect handling of IPv6 when enabling Anonymous FTP in Plesk. The key point here is that Plesk does not officially support Anonymous FTP over IPv6.
Because of this, instead of showing a proper message, Plesk was throwing a 500 error when trying to set up Anonymous FTP on an IPv6-enabled domain.
To address this, the Plesk development team has created a bug report: PPPM-14800.

Additionally, if you would like to see official IPv6 support for Anonymous FTP in future Plesk releases, you can submit a feature request here:
UserVoice: Anonymous FTP Access via IPv6
Plesk prioritizes the most popular suggestions, so your feedback is valuable.

So for me the mystery with the error message has been solved for now, as I don't use Anonymous FTP over IPv6 I can live like this until a permanent fix is published.

Thank you for the great support

R.Sivgin

 

[emilyy3]

So guys,

I had great support from the Plesk team today,
The problem appears to have been temporarily fixed with a patch.
I was informed that the Plesk Development team is aware of the issue and actively working on a permanent fix.
For more details and updates, users can always check the official Plesk changelog here: https://docs.plesk.com/release-notes/obsidian/change-log/

The issue was caused by incorrect handling of IPv6 when enabling Anonymous FTP in Plesk. The key point here is that Plesk does not officially support Anonymous FTP over IPv6.
Because of this, instead of showing a proper message, Plesk was throwing a 500 error when trying to set up Anonymous FTP on an IPv6-enabled domain.
To address this, the Plesk development team has created a bug report: PPPM-14800.

Additionally, if you would like to see official IPv6 support for Anonymous FTP in future Plesk releases, you can submit a feature request here:
UserVoice: Anonymous FTP Access via IPv6
Plesk prioritizes the most popular suggestions, so your feedback is valuable.

So for me the mystery with the error message has been solved for now, as I don't use Anonymous FTP over IPv6 I can live like this until a permanent fix is published.

Thank you for the great support

R.Sivgin
View attachment 27800

I also have the same question because I’m facing a very similar issue on my setup. Everything works fine with FTPS connections through WinSCP using normal user credentials, but clicking on Anonymous FTP immediately throws a 500 Type Error. I already tried running the Diagnosis & Repair tools and checked the basic configuration, but I still can’t figure out if this is caused by a server configuration problem or some kind of bug. Hopefully someone here can clarify what’s causing it.

 

[Sebahat.hadzhi]

@emilyy3 , if you have the website/subscription configured with IPv6, this is expected behavior. Anonymous FTP on IPv6 is not supported as explained by @cobanramo. If it's not configured with Ipv6, the issue you are experiencing is likely different, so please open a dedicated thread.

 

[emilyy3]

So guys,

I had great support from the Plesk team today,
The problem appears to have been temporarily fixed with a patch.
I was informed that the Plesk Development team is aware of the issue and actively working on a permanent fix.
For more details and updates, users can always check the official Plesk changelog here: https://docs.plesk.com/release-notes/obsidian/change-log/

The issue was caused by incorrect handling of IPv6 when enabling Anonymous FTP in Plesk. The key point here is that Plesk does not officially support Anonymous FTP over IPv6.
Because of this, instead of showing a proper message, Plesk was throwing a 500 error when trying to set up Anonymous FTP on an IPv6-enabled domain.
To address this, the Plesk development team has created a bug report: PPPM-14800.

Additionally, if you would like to see official IPv6 support for Anonymous FTP in future Plesk releases, you can submit a feature request here:
UserVoice: Anonymous FTP Access via IPv6
Plesk prioritizes the most popular suggestions, so your feedback is valuable. Interestingly, while troubleshooting this issue, I noticed some similarities with the way authentication and network handling problems are often discussed in frp bypass 2026 communities, where unsupported configurations or protocol conflicts can trigger unexpected verification or connection errors until a proper patch is released.

So for me the mystery with the error message has been solved for now, as I don't use Anonymous FTP over IPv6 I can live like this until a permanent fix is published.

Thank you for the great support

R.Sivgin
View attachment 27800

Thanks for the clarification. That actually helps narrow things down. My setup does have IPv6 enabled, so it makes sense now why Anonymous FTP is failing while normal FTPS logins through WinSCP continue to work correctly. I wasn’t aware that Anonymous FTP over IPv6 is currently unsupported, so I appreciate the explanation. I’ll test again with IPv6 disabled or on an IPv4-only configuration just to confirm the behavior on my side. Thanks again for pointing me in the right direction.