A vulnerability in Apache Kerby allows bypassing the Kerberos pre-authentication check by sending a Pre-Authentication Data (PA-DATA) packet with an unrecognized or unsupported type. This flaw enables attackers to circumvent the initial authentication step, potentially leading to unauthorized access or impersonation within Kerberos-protected environments. The issue affects versions prior to 2.1.2. A fix is available in version 2.1.2.