The recv_files function in receiver.c in the daemon in rsync 3.1.2, and 3.1.3-development before 2017-12-03, proceeds with certain file metadata updates before checking for a filename in the daemon_filter_list data structure, which allows remote attackers to bypass intended access restrictions.
https://www.debian.org/security/2017/dsa-4068
https://lists.debian.org/debian-lts-announce/2017/12/msg00020.html
https://git.samba.org/?p=rsync.git%3Ba=commit%3Bh=3e06d40029cfdce9d0f73d87cfd4edaf54be9c51
https://bugzilla.redhat.com/show_bug.cgi?id=1522874#c4
http://security.cucumberlinux.com/security/details.php?id=169