RFC 2744 permits a GSS-API implementation to delete an existing security context on a second or subsequent call to gss_init_sec_context() or gss_accept_sec_context() if the call results in an error.  This API behavior has been found to be dangerous, leading to the possibility of memory errors in some callers.  For safety, GSS-API implementations should instead preserve existing security contexts on error until the caller deletes them.

References:

http://krbdev.mit.edu/rt/Ticket/Display.html?id=8598

Upstream patch:

https://github.com/krb5/krb5/commit/56f7b1bc95a2a3eeb420e069e7655fb181ade5cf