But the others don't seem very likely either -
- Saul was the one who put Quinn on the overall hit man job, but it's all but unimaginable that Saul now wants to kill Carrie. It would be an insanely unexpected twist, with the emphasis on insane. It can't be Saul.
- Dar is a suitably dislikable character. He certainly has the clout to issue such an order. But he's far too obvious a choice.
- The only other person I can think of off-hand is the now fired CIA head in Germany. But how would she be able to break into Saul's system? And she seems too lightweight to play such a pivotally powerful position in our story.
- Hackers - perhaps one of whom we've already seen (or not), knew enough to crack the CIA code, and issue the order, and make it appear that it came from Saul. I have no idea if the savvy to do this is on the same level as what was needed to lay bare the US-German digital correspondence.
- CIA biggies back in the US - other than Dar, I'm assuming there are others in that room we saw in the first episode who have the wherewithal, and could command the tech support, to issue a kill on Carrie. I have no specific idea just who that could be, though.
And see also Homeland on Showtime ... Homeland 1.8: Surprises ... Homeland Concludes First Season: Exceptional
different kind of espionage