To be fair unless Iran or Russia hands them fairly high end SAM's they're not reaching the 35,000+ that an airliner is going at; that's fairly specialist stuff.
Its why they kept flying over Ukraine; they thought it almost impossible that Rebels or the Ukrainian Army had anything capable of that height.
Yup - unless someone has smuggled something in nothing of that capability exists in Afghanistan - but some of the surrounding countries do so a very long shot it could happen if something was stolen and smuggled in.