CVE-2016-1000027 identifies a critical unsafe Java deserialization vulnerability in Pivotal Spring Framework versions before 6.0.0 that enables remote code execution when processing untrusted data through HTTP invoker components. This vulnerability achieves a maximum CVSS score of 9.8 (Critical severity) with an EPSS score of 97.7 percentile and 49.4% exploitation probability, indicating extremely high risk for Java applications utilizing Spring Framework's HTTP invoker functionality. The vulnerability details reveal that the HttpInvokerServiceExporter class contains unsafe deserialization methods in readRemoteInvocation() that fail to properly validate untrusted objects before processing, allowing attackers to execute arbitrary code through crafted serialized payloads. This creates substantial exploit risk for enterprise Java applications using Spring Framework for remote method invocation, particularly affecting systems that expose HTTP invoker endpoints to untrusted clients or process user-controlled serialized data through Spring's remoting capabilities. The technical root cause lies in Spring Framework's HttpInvokerServiceExporter and SimpleHttpInvokerServiceExporter classes, where the readRemoteInvocation() methods directly deserialize input streams without proper validation, creating a vector for known exploited vulnerabilities targeting Java deserialization flaws. The vulnerability specifically affects the doReadRemoteInvocation() method within RemoteInvocationSerializingExporter, where the critical ObjectInputStream.readObject() call occurs without security controls, enabling attackers to instantiate malicious objects and achieve code execution. Spring maintainers have taken a unique position, treating this as a documentation issue rather than a security flaw, arguing that deserialization of untrusted data was never an intended use case. Mitigation strategies include upgrading to Spring Framework 6.0.0 which removes vulnerable classes entirely, or implementing workarounds such as restricting HTTP invoker endpoint access to trusted clients only and utilizing alternative message formats like JSON instead of Java serialization. Organizations should prioritize identifying all applications using Spring Framework HTTP invokers, implement strict network controls to prevent untrusted access to remoting endpoints, consider migrating to safer communication protocols, and maintain updated CVE database records to track similar deserialization vulnerabilities that could compromise Java application security through unsafe object instantiation and remote method invocation attacks.