A deserialization issue in Kibana can lead to arbitrary code execution when Kibana attempts to parse a YAML document containing a crafted payload. A successful attack requires a malicious user to have a combination of both specific Elasticsearch indices privileges https://www.elastic.co/guide/en/elasticsearch/reference/current/defining-roles.html#roles-indices-priv and Kibana privileges https://www.elastic.co/guide/en/fleet/current/fleet-roles-and-privileges.html assigned to them.
The following Elasticsearch indices permissions are required
Any of the following Kibana privileges are additionally required
The product deserializes untrusted data without sufficiently verifying that the resulting data will be valid.
It is often convenient to serialize objects for communication or to save them for later use. However, deserialized data or code can often be modified without using the provided accessor functions if it does not use cryptography to protect itself. Furthermore, any cryptography would still be client-side security – which is a dangerous security assumption. Data that is untrusted can not be trusted to be well-formed. When developers place no restrictions on “gadget chains,” or series of instances and method invocations that can self-execute during the deserialization process (i.e., before the object is returned to the caller), it is sometimes possible for attackers to leverage them to perform unauthorized actions, like generating a shell.