Microsoft Windows 7 SP1, Windows Server 2008 SP2 and R2 SP1, Windows 8.1 and Windows RT 8.1, Windows Server 2012 and R2, Windows 10 Gold, 1511, 1607, and 1703, and Windows Server 2016 allows an attacker to bypass Extended Protection for Authentication when Kerberos fails to prevent tampering with the SNAME field during ticket exchange, aka "Kerberos SNAME Security Feature Bypass Vulnerability" or Orpheus' Lyre.