zsh through version 5.4.2 is vulnerable to a stack-based buffer overflow in the utils.c:checkmailpath function. A local attacker could exploit this to execute arbitrary code in the context of another user.

Zsh before version 5.4.2-test-1 is vulnerable to a buffer overflow in the shell autocomplete functionality. A local unprivileged user can create a specially crafted directory path which leads to code execution in the context of the user who tries to use autocomplete to traverse the before mentioned path. If the user affected is privileged, this leads to privilege escalation.

zsh through version 5.4.2 is vulnerable to a stack-based buffer overflow in the exec.c:hashcmd() function. A local attacker could exploit this to cause a denial of service.

In exec.c in zsh before 5.0.7, there is a buffer overflow for very long fds in the ">& fd" syntax.

In utils.c in zsh before 5.4, symlink expansion had a buffer overflow.

In params.c in zsh through 5.4.2, there is a crash during a copy of an empty hash table, as demonstrated by typeset -p.

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.

In subst.c in zsh through 5.4.2, there is a NULL pointer dereference when using ${(PA)...} on an empty array result.

In zsh before 5.3, an off-by-one error resulted in undersized buffers that were intended to support PATH_MAX characters.

In utils.c in zsh before 5.0.6, there is a buffer overflow when scanning very long directory paths for symbolic links.