This indicates an attack attempt to exploit a Denial of Service vulnerability in MIT Kerberos.
The vulnerability is due to an NULL pointer dereference error when vulnerable module handles an invalid token inside GSSAPI related packets. A remote attacker may be able to exploit this to cause a denial of service condition on the affected system through injecting an invalid token during a valid session.
MIT Kerberos git prior to fb99962cbd063ac04c9a9
Denial of Service: Remote attackers can crash vulnerable systems or services
Apply the most recent upgrade or patch from the vendor.