The MITRE CVE dictionary describes this issue as:
The process_tgs_req function in do_tgs_req.c in the Key Distribution Center (KDC) in MIT Kerberos 5 (aka krb5) 1.9 through 1.9.2 allows remote authenticated users to cause a denial of service (NULL pointer dereference and daemon crash) via a crafted TGS request that triggers an error other than the KRB5_KDB_NOENTRY error.
Find out more about CVE-2011-1530 from the
MITRE CVE dictionary dictionary and
Not vulnerable. This issue did not affect the versions of krb5 as shipped with Red Hat Enterprise Linux 4 and 5.