A untrusted search path issue was found in Calibre at devices/linux_mount_helper.c leading to the ability of unprivileged users to execute any program as root.
gui2/viewer/bookmarkmanager.py in Calibre 3.18 calls cPickle.load on imported bookmark data, which allows remote attackers to execute arbitrary code via a crafted .pickle file, as demonstrated by Python code that contains an os.system call.