You have performed a vulnerability scan on your website and the report specifies that some one or more packages (e.g. OpenSSH / Apache) are not secure as vulnerabilities were fixed in later versions than the ones Acquia has installed.
Acquia uses packages from the Ubuntu repositories. Canonical (the "upstream" vendor) patches software like OpenSSH / Apache... in their repos in order to fix reported vulnerabilities, but they typically don't update to newer versions (which might cause compatibility problems etc..) especially in the Long Term Support (LTS) releases of Ubuntu which Acquia uses.
This means that looking at version numbers alone can suggest that Acquia servers are running an old version which has vulnerabilities - for example where the problem is described as applying to "OpenSSH_7.2p2 and prior". This is usually incorrect as Canonical / Ubuntu has patched the vulnerabilities upstream.
Canonical maintains a CVE tracker which can be used to check the status of patching for specific vulnerabilities. For example, current openSSH CVEs are tracked here : https://ubuntu.com/security/cve?package=openssh
You might also want to consult the following documentation https://docs.acquia.com/cloud-platform/arch/security/#cloud-lamp-security.