RADIUS Protocol under RFC 2865 is susceptible to forgery attacks by a local attacker who can modify any valid Response (Access-Accept, Access-Reject, or Access-Challenge) to any other response using a chosen-prefix collision attack against MD5 Response Authenticator signature.
modules/rlm_unix/rlm_unix.c in FreeRADIUS before 2.2.0, when unix mode is enabled for user authentication, does not properly check the password expiration in /etc/shadow, which allows remote authenticated users to authenticate using an expired password.