StartEncrypt Vulnerabilities

In my last post I wrote about StartCom’s new StartEncrypt service and its misleading advertisement email. In it I mentioned that they were not using the ACME protocol that Let’s Encrypt is using, but their own StartAPI protocol, for which documentation is behind a login. Their client was also not open source.

It didn’t take long for the first security issues to be found. Computest found multiple vulnerabilities in the StartEncrypt API and client, the most critical of which allowed the user to fetch certificates for domains outside their control. Domains like, etc. The following quotes speak volumes about the security of StartEncrypt:

A malicious client can specify a path to any file on the server for which a certificate is requested. This means that, for example, anyone can obtain a certificate for sites like and where users can upload their own files.


The client doesn’t check the server’s certificate for validity when connecting to the API, which is pretty ironic for an SSL tool.

As Computest points out, when a certificate authority publishes a service which such problems, they are undermining the thing they are paid for – the trustworthiness of their certificates. Personally, after the latest events with StartEncrypt, I would no longer recommend StartCom to anyone, for neither paid nor free certificates.