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.

An issue was discovered in zsh before 5.6. Shebang lines exceeding 64 characters were truncated, potentially leading to an execve call to a program name that is a substring of the intended one.

An issue was discovered in zsh before 5.6. The beginning of a #! script file was mishandled, potentially leading to an execve call to a program named on the second line.