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.
https://github.com/krb5/krb5/commit/a7886f0ed1277c69142b14a2c6629175a6331edc
https://github.com/krb5/krb5/commit/524688ce87a15fc75f87efc8c039ba4c7d5c197b
https://exchange.xforce.ibmcloud.com/vulnerabilities/95210
https://bugzilla.redhat.com/show_bug.cgi?id=1121877
http://www.securitytracker.com/id/1030706
http://www.securityfocus.com/bid/69160
http://www.mandriva.com/security/advisories?name=MDVSA-2014:165
http://www.debian.org/security/2014/dsa-3000
http://support.f5.com/kb/en-us/solutions/public/15000/500/sol15561.html
http://secunia.com/advisories/61051
http://secunia.com/advisories/60448
http://secunia.com/advisories/60082
http://secunia.com/advisories/59102
http://rhn.redhat.com/errata/RHSA-2015-0439.html
http://lists.fedoraproject.org/pipermail/package-announce/2014-August/136360.html
http://krbdev.mit.edu/rt/Ticket/Display.html?id=7970
http://aix.software.ibm.com/aix/efixes/security/nas_advisory1.asc