In utils.c in zsh before 5.4, symlink expansion had a buffer overflow.
https://usn.ubuntu.com/3593-1/
https://sourceforge.net/p/zsh/code/ci/c7a9cf465dd620ef48d586026944d9bd7a0d5d6d
https://security.gentoo.org/glsa/201805-10
https://lists.debian.org/debian-lts-announce/2020/12/msg00000.html