Get value from agent failed: TCP successful, cannot establish TLS timed out

[Gijs007]

I've a fresh Zabbix 5.0.3 installation on Ubuntu 20.04. (Came from Zabbix 4.0.22 on Ubuntu 18.04)
On the new deployment I'm getting some strange errors when sending remote commands to the Zabbix agent. (incoming passive and active check data is coming in fine however)

The Zabbix server reports: Get value from agent failed: TCP successful, cannot establish TLS to [[ZABBIX_AGENT_IP]:10050]: SSL_connect() timed out
The Zabbix agent log shows the following entries: 4520:20200918:054401.601 failed to accept an incoming connection: from ZABBIX_MASTER_IP: unspecified certificate verification error: TLS handshake set result code to 5:

I'm using PSK's for encryption, for connections to and from the host.

What I've already tried: updating some of the Zabbix agent to the latest version (5.0.3), but this didn't help. Note that the agents are running on Windows.
I doubt the issue is with the agents, as they were working fine with the old Zabbix installation and should be compatible even when not updated.

Does anyone know what the issue could be? It looks like a bug to me.

[tim.mooney]

Not certain, but is this possibly related: https://www.zabbix.com/forum/zabbix-...-openssl-1-1-1

It's hard to see how active & passive would be OK but remote commands wouldn't if the problem were related to the key length, but it's something that you could potentially "easily" rule out by trying keys that meet that limit.

[Gijs007]

Thank you for the suggestion. I'm using a 64 character PSK, which should be exactly 512 bits.
I suspect this is some kind of bug, most likely in the Zabbix server, when sending remote commands. What would be the proper way to get the attention of the Zabbix developers?

[tim.mooney]

A few developers and support people visit these forums, but the best way to report an issue that you think may be a bug is https://support.zabbix.com