When a libcurl-based application performs transfers via "SCP://" or "SFTP://" and utilizes the "CURLOPT_SSH_KEYFUNCTION" callback, it may silently accept an untrusted server. This vulnerability occurs when a server presents a host key type that does not match the specific key type already recorded for that host in the "known_hosts" file. Instead of rejecting the mismatch, the callback mechanism fails to properly enforce the restriction, allowing the connection to succeed without warning and risking a potential man-in-the-middle attack.