% sudo freebsd-update fetch
Looking up update.FreeBSD.org mirrors... 4 mirrors found.
Fetching metadata signature for 10.3-RELEASE from update4.freebsd.org... done.
Fetching metadata index... done.

The update metadata is correctly signed, but
failed an integrity check.
Cowardly refusing to proceed any further.

うーむ
% freebsd-version
10.3-RELEASE
-questions 読むと同じ症状あり