Proxmox node certificate

[jindalcdac]

Hello everyone,

I recently wanted to understand the impact of an expired certificate on a Proxmox node and on a Proxmox cluster. To test this, I modified the certificate validity period so that the node certificate expired yesterday.

After the certificate expired, I observed the following:

• I am still able to access the Proxmox web GUI.
• API calls continue to work.
• The cluster remains healthy.
• VM live migration is working as expected.
• VM creation is working.
• Encrypted HTTPS communication is still taking place (the browser shows a certificate warning, but traffic remains encrypted).

This made me wonder about the practical role of the node certificate in Proxmox.

My understanding was that an expired certificate would have a larger impact on node management or cluster operations, but in my testing everything appears to function normally apart from browser trust warnings.

I have a few questions:

1. What functionality in Proxmox actually depends on the node certificate being valid?
2. Why do cluster operations such as migration and VM management continue to work even after the certificate expires?
3. Is the primary consequence of expiration simply the loss of trust/identity verification rather than a loss of encryption?
4. Is there a way to configure a browser so that it completely refuses access to the Proxmox GUI when the certificate is expired instead of allowing users to bypass the warning?
5. Would HSTS (HTTP Strict Transport Security) have any effect in this scenario, or does it only prevent users from bypassing certificate errors under specific conditions?

I would appreciate any insights into how Proxmox uses certificates internally and what the real-world risks are when a node certificate expires.

Thank you.

 

[YaZoal]

3. Is the primary consequence of expiration simply the loss of trust/identity verification rather than a loss of encryption?

Exactly.
If your certificate expires, it’s essentially no different from a self-signed certificate. You will need to explicitly trust it in order to continue using the GUI. The cluster should continue to work properly.

 

[jindalcdac]

Exactly.
If your certificate expires, it’s essentially no different from a self-signed certificate. You will need to explicitly trust it in order to continue using the GUI. The cluster should continue to work properly.

So what is the use of certificate if it is expired and GUI still working fine?

 

[YaZoal]

An expired certificate still encrypts your data, but you lose the ability to trust who you are talking to [0], e.g Man-in-the-Middle (MITM) attacks possible.

[0] https://www.crowdstrike.com/en-us/blog/the-risks-of-expired-ssl-certificates/