Use-after-free vulnerability in kadmin/server/server_stubs.c in kadmind in MIT Kerberos 5 (aka krb5) 1.5 through 1.6.3 allows remote authenticated users to cause a denial of service (daemon crash) via a request from a kadmin client that sends an invalid API version number.
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.