LibreSSL 2.5.1 to 2.5.3 lacks TLS certificate verification if SSL_get_verify_result is relied upon for a later check of a verification result, in a use case where a user-provided verification callback returns 1, as demonstrated by acceptance of invalid certificates by nginx.
https://trac.nginx.org/nginx/ticket/1257
https://github.com/libressl-portable/portable/issues/307