Vault attempts to protect against host compromise scenarios, but it's a very hard problem. Ultimately, in order to do anything useful, Vault deals with plaintext values in memory, and that means that yes, there are ways for an attacker to get access.

Here's a good example: https://github.com/slingamn/vault-exfiltrate

The Vault docs include a list of 'hardening' steps for secure production usage. These are great steps to take, but each one represents a mistake that could be made. And because the Vault process is trusted with plaintext secrets, the stakes are high. Making a mistake could lead to a compromise.

With EnvKey, the host server is never sent secrets in plaintext. For defense in depth, we also follow best practices for hardening our networks. But I think we've seen with Okta and other incidents that despite best intentions, best efforts, and strong engineering, trusting the host server whatsoever just isn't good enough anymore.