pacman before 5.2 is vulnerable to arbitrary command injection in conf.c in the download_with_xfercommand() function. This can be exploited when unsigned databases are used. To exploit the vulnerability, the user must enable a non-default XferCommand and retrieve an attacker-controlled crafted database and package.
pacman before 5.2 is vulnerable to arbitrary command injection in lib/libalpm/sync.c in the apply_deltas() function. This can be exploited when unsigned databases are used. To exploit the vulnerability, the user must enable the non-default delta feature and retrieve an attacker-controlled crafted database and delta file.