Integer overflow in the decode_digit function in puny_decode.c in Libidn2 before 2.0.4 allows remote attackers to cause a denial of service or possibly have unspecified other impact.
https://lists.debian.org/debian-lts-announce/2018/07/msg00040.html
https://gitlab.com/libidn/libidn2/commit/3284eb342cd0ed1a18786e3fcdf0cdd7e76676bd