An issue was discovered in NeoMutt before 2018-07-16. nntp_add_group in newsrc.c has a stack-based buffer overflow because of incorrect sscanf usage.
https://www.debian.org/security/2018/dsa-4277
https://neomutt.org/2018/07/16/release
https://lists.debian.org/debian-lts-announce/2018/08/msg00001.html
https://github.com/neomutt/neomutt/commit/6296f7153f0c9d5e5cd3aaf08f9731e56621bdd3