In 2016 I fuzzed awk and found a bunch of segfaults. Sadly it seems still not fixed:

      $ ./bin/gawk -V | head -n 1
      GNU Awk 5.0.0, API: 2.0

      $ ./bin/gawk 'for (i = ) in steve kemp rocks'
      gawk: cmd. line:1: for (i = ) in steve kemp rocks
      gawk: cmd. line:1: ^ syntax error
      gawk: cmd. line:1: for (i = ) in steve kemp rocks
      gawk: cmd. line:1:          ^ syntax error
      gawk: cmd. line:1: fatal error: internal error
      Aborted (core dumped)

I'll have to forward bugs from the Debian-tracker to the maintainers directly I guess.