ALAS2-2018-986

NULL dereference in cd in sh compatibility mode under given circumstances
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. (CVE-2017-18205)

Null-pointer deref when using ${(PA)...} on an empty array result:
In subst.c in zsh through 5.4.2, there is a NULL pointer dereference when using ${(PA)...} on an empty array result. (CVE-2018-7548)

Buffer overrun in xsymlinks
In utils.c in zsh before 5.4, symlink expansion had a buffer overflow. (CVE-2017-18206)

Crash on copying empty hash table
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. (CVE-2018-7549)

src:
    zsh-5.3.1-7.amzn2.src

x86_64:
    zsh-5.3.1-7.amzn2.x86_64
    zsh-html-5.3.1-7.amzn2.x86_64
    zsh-debuginfo-5.3.1-7.amzn2.x86_64