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.

Minor correction, but that bug was never in any "official" coreutils release. The bug was in a multi-byte character patch that many distributions use (and still use). There have been other CVEs in that patch [1].

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)

Not saying that both issues don't deserve fixing. But I wouldn't really panic over either of them.

[1] https://lwn.net/Articles/535735/