Icinga 2 is an open source monitoring system. From 2.10.0 to before 2.15.1, 2.14.7, and 2.13.13, when creating an invalid reference, such as a reference to null, dereferencing results in a segmentation fault. This can be used by any API user with access to an API endpoint that allows specifying a filter expression to crash the Icinga 2 daemon. A fix is included in the following Icinga 2 versions: 2.15.1, 2.14.7, and 2.13.13.