In some cases it was possible to crash (overflow) sort.c, not just DoS. I did try to look more info the issue - it was not handled for quite some time however I did not find any real world impact.
But the worst you can do is crash 'sort' with that. Note that uutils also has crashes. Here is one due to unbounded recursion:
$ ./target/release/coreutils mkdir -p `python3 -c 'print("./" + "a/" * 32768)'`
Segmentation fault (core dumped)