In Apache Ignite before 2.4.8 and 2.5.x before 2.5.3, the serialization mechanism does not have a list of classes allowed for serialization/deserialization, which makes it possible to run arbitrary code when 3-rd party vulnerable classes are present in Ignite classpath. The vulnerability can be exploited if the one sends a specially prepared form of a serialized object to GridClientJdkMarshaller deserialization endpoint.