Thank you.

Difficult as in unlikely that the exploit works or difficult to write an exploit? The latter doesn't help me much. :)

Regarding the php2shell issue: a lot of admins took their services down until it was patched. It's more a decision based on a guess - big number bad, evil acronym scary - than actually understanding what the exploit does. One can either believe it or not.

And that's the thing about the recent exploit (multipath TCP): I can't evaluate myself, whether the issue is likely an exploitable RCE. That is one factor missing in risk assessment: is the outcome potentially fatal? Yes, rce and priv escalation. Is it likely? I can't tell.

I'm sorry. I don't mean to doubt your expertise. I simply don't know you. It is the same with hackernews, the author repeats what he's or she's told. (Good overview article though. Thanks again for it.) RN It's: Someone from the internet said don't panic. A link to a statement from the Ubuntu package maintainer or distribution would make me feel at ease. I still couldn't make sure for myself - a lack of time and competence in the field - but I would trust it.