In builtin.c in zsh before 5.4, when sh compatibility mode is used, there is a NULL pointer dereference during processing of the cd command with no argument if HOME is not set.
Exploitability
AV:NAC:HPR:NUI:NScope
S:UImpact
C:HI:HA:H8.1/CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H