The acc_ctx_cont function in the SPNEGO acceptor in
lib/gssapi/spnego/spnego_mech.c in MIT Kerberos 5 (aka krb5) 1.5.x through
1.12.x before 1.12.2 allows remote attackers to cause a denial of service
(NULL pointer dereference and application crash) via an empty continuation
token at a certain point during a SPNEGO negotiation.