A "fatal flaw" which is neither a fatal, nor a flaw.

The article in SC Magazine talks about "security flaws" in Kerberos protocol.  But what are those flaws about?

If we dig deeper, the only phrase in the article suggests that "if the attacker knows user's secret key, he can replay authentication without the need for user's password". Actually this is not a flaw. If the attacker got to user's secret key somehow, the user and the network are already in trouble, because this means that the attacker has already found some flaws elsewhere.

Now, Kerberos' shortcomings and disadvantages were known for years, and the discussed one was known as well. This is why Kerberos is not recommended and is replaced by modern protocols like SAML and OAuth even in intranets.

To sum it up, digging the grave and finding old flaws and bringing them back to the sunlight is an easy way to establish yourself as a security researcher, but you still need to look at the roots. And protection of credentials and use of multifactor authentication are the things that separate good security from the bad one.