Double free vulnerability in the GSS-API library (lib/gssapi/krb5/k5unseal.c), as used by the Kerberos administration daemon (kadmind) in MIT krb5 before 1.6.1, when used with the authentication method provided by the RPCSEC_GSS RPC library, allows remote authenticated users to execute arbitrary code and modify the Kerberos key database via a message with an "an invalid direction encoding".