Sessions between a rock and a hard place.
On the one hand, he knows that if he does this that McCabe has rights, and that a lawsuit or an investigation will follow, which will expose this criticism of him for what it is. That would be bad for Sessions.
On the other hand, I promise you that Trump and his people are all over Sessions demanding that he fire McCabe so as to perpetuate the narrative that the FBI was anti-Trump from the get go.
If Sessions chooses the option not to act on it, Fox can still run stories about it. Trump can still tweet about it. And the base will eat it up. If he gets mad enough, Trump might fire him, though, so that's a negative.
If he chooses the option to fire McCabe, it opens the whole can of worms up and the partisan nature of this report will be exposed, along with Trump and Sessions.
Smart money says that in the end he does not act on it. But that it still gets used by the right to pretend that there were shenanigans.