Cyrus IMAP before 3.0.3 allows remote authenticated users to write to arbitrary files via a crafted (1) SYNCAPPLY, (2) SYNCGET or (3) SYNCRESTORE command.
https://www.cyrusimap.org/imap/download/release-notes/3.0/x/3.0.3.html
https://github.com/cyrusimap/cyrus-imapd/commit/5edadcfb83bf27107578830801817f9e6d0ad941
https://github.com/cyrusimap/cyrus-imapd/commit/53c4137bd924b954432c6c59da7572c4c5ffa901