It was found that versions of rpm before 4.13.0.2 use temporary files with predictable names when installing an RPM. An attacker with ability to write in a directory where files will be installed could create symbolic links to an arbitrary location and modify content, and possibly permissions to arbitrary files, which could be used for denial of service or possibly privilege escalation.
https://security.gentoo.org/glsa/201811-22
https://github.com/rpm-software-management/rpm/commit/404ef011c300207cdb1e531670384564aae04bdc