The key fingerprint headline has unsymmetrical braces for ED25519 in 6.6p1: +--[ED25519 256--+ | ... | Seems like in key.c:561, snprintf aborts before being able to put the final ']'. Note, that there's an unnecessary ' ' in there because of ED25519's short key_size. Reducing the minimum field width for key_size(k) in snprintf from 4 to 3 should remove the unnecessary ' ' and make room for the missing ']'.
*** This bug has been marked as a duplicate of bug 2247 ***
Set all RESOLVED bugs to CLOSED with release of OpenSSH 7.1