WildFly Elytron password implementations (wildfly-elytron-password-impl, all supported versions reported) apply Unicode Normalization Form KC (NFKC) in AbstractPasswordImpl.getNormalizedPasswordBytes() before hashing and verification (BCrypt, SCRAM, Unix crypts, and related). NFKC compatibility mapping collapses fullwidth Latin characters (e.g. U+FF01–U+FF5E) to their ASCII equivalents, so a password the user believed contained non-ASCII fullwidth characters is stored and verified as the ASCII form. An attacker can therefore match such passwords with an ASCII-only dictionary. This is older SASLprep-style processing; modern PRECIS OpaqueString (RFC 8265) uses NFC and does not width-map passwords. CWE-173.