The TLS session cache in FreeRADIUS 2.1.1 through 2.1.7, 3.0.x before 3.0.14, 3.1.x before 2017-02-04, and 4.0.x before 2017-02-04 fails to reliably prevent resumption of an unauthenticated session, which allows remote attackers (such as malicious 802.1X supplicants) to bypass authentication via PEAP or TTLS.