I’ve written extensively about how public TLS certificate lifetimes will drop to just 47 days by March 2029. Before then, we’ll see certificate lifetimes gradually drop from the current 398 days to 200 days on March 15, 2026, and then to 100 days on March 15, 2027. In preparation for this, I’ve been working with many customers to deploy automated certificate enrollment and renewal solutions to eliminate the need for manual intervention. Interestingly, Let’s Encrypt now offers extremely short-lived certificates that are good for just 6 days! While they work just fine for Always On VPN, I discovered they will not work for DirectAccess.
6-Day Certificate
After successfully enrolling for a 6-day TLS certificate from Let’s Encrypt (I used CertKit, BTW!), I encountered an error when trying to assign the short-lived certificate to the IP-HTTPS listener in the DirectAccess configuration. Specifically, when running the Set-RemoteAccess PowerShell command, I received the following error.
Set-RemoteAccess: The parameter is incorrect.
Further investigation showed that I could install other public TLS certificates just fine. For some reason, though, DirectAccess did not like this new 6-day certificate.
Missing Subject Name
After digging a bit deeper, I realized the Subject field of the new 6-day Let’s Encrypt certificate was empty.
Subject vs. SAN in Modern TLS
Modern TLS clients rely entirely on the Subject Alternative Name (SAN) field for identity validation, and the older practice of matching against the certificate’s Subject field has been phased out for many years. Many certificate authorities, including Let’s Encrypt, now leave the Subject field empty because it no longer serves a functional purpose in current TLS implementations. DirectAccess still expects this field to contain data and does not properly fall back to SAN‑only validation. As a result, any certificate with an empty Subject field, such as the new 6‑day certificates from Let’s Encrypt, will fail when applied to the DirectAccess IP‑HTTPS listener.
Workaround
Admittedly, using 6-Day public TLS certificates for DirectAccess is extreme and likely overkill for this workload. The good news is that DirectAccess still works perfectly with 90-day Let’s Encrypt certificates, so the lack of 6-day certificate support should not be impactful.
CertKit
Have you heard about CertKit? CertKit, an online service for automating Let’s Encrypt certificate enrollment and renewal, has added support for Always On VPN and DirectAccess. Find details on leveraging it for public TLS certificates for these solutions here.
Additional Information
Always On VPN SSTP with Let’s Encrypt Certificates
Always On VPN and 47-Day Public TLS Certificates
The Case for Short-Lived Certificates in Enterprise Environments
CertKit Agent Support for Always On VPN SSTP and DirectAccess IP-HTTPS TLS Certificates
