CVE-2026-59306 in Spring Cloud Stream
Summary
by MITRE • 08/27/2026
Potential for deserialization of untrusted types in Spring Cloud Stream. Spring Cloud Stream 5.0.0 - 5.0.2 Spring Cloud Stream 4.3.0 - 4.3.3 Spring Cloud Stream 4.2.0 - 4.2.6
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Analysis
by VulDB Data Team • 08/27/2026
Spring Cloud Stream is a framework designed to build event-driven microservices, enabling developers to connect external message brokers with minimal effort by providing configuration abstractions for producers and consumers. The vulnerability identified in versions ranging from Spring Cloud Stream 5.0.0 through 5.0.2 and 4.3.0 through 4.3.3 centers on the framework's handling of serialized data during deserialization processes. Specifically, the issue arises when the application accepts untrusted input streams that are processed using Java serialization mechanisms without sufficient validation or restriction on the types allowed for instantiation. This flaw allows an attacker to craft malicious payloads containing specially constructed objects that, upon being deserialized by the vulnerable component, can trigger arbitrary code execution within the context of the running application.
The technical root cause lies in the reliance on standard Java ObjectInputStream capabilities which inherently support polymorphic type resolution during deserialization. When a consumer receives a message from an external source or broker, it may attempt to convert the byte stream back into a Java object. If the framework does not strictly enforce allowlists for permitted classes or if default serialization is used without protective filters, an attacker can supply serialized data representing dangerous gadget chains. These chains typically involve common libraries present in most enterprise environments, such as Apache Commons Collections or various scripting engines, which contain methods that execute system commands or perform other privileged operations when invoked during the deserialization process. This aligns with CWE-502, Deserialization of Untrusted Data, a critical weakness where software fails to validate data before using it, leading to potential remote code execution.
From an operational perspective, this vulnerability poses a severe risk to the integrity and availability of microservices relying on Spring Cloud Stream for inter-service communication or event processing. An attacker who can inject messages into the message broker or intercept traffic between services could exploit this flaw to gain full control over the affected server. This compromise extends beyond simple data theft; it enables lateral movement within the network, privilege escalation if the application runs with elevated permissions, and potential disruption of critical business workflows dependent on real-time event processing. The impact is particularly acute in environments where message brokers are accessible from untrusted networks or when third-party services contribute events to shared streams without rigorous authentication and integrity checks.
Mitigation strategies must focus on preventing the execution of arbitrary code during deserialization while maintaining necessary functionality for legitimate data exchange. The primary recommendation is to upgrade to a patched version of Spring Cloud Stream that implements stricter type checking mechanisms, such as using Jackson with safe configuration or replacing Java serialization with safer alternatives like JSON or Protocol Buffers where possible. For applications unable to immediately upgrade, implementing a custom ObjectInputFilter can restrict the classes allowed during deserialization by defining an allowlist of trusted types and blocking all others. Additionally, organizations should enforce strict access controls on message brokers, ensure that only authenticated services can publish messages, and monitor for anomalous patterns in serialized data payloads using intrusion detection systems capable of identifying known gadget chain signatures associated with ATT&CK technique T1059 Command and Scripting Interpreter or T1203 Exploitation for Client Execution.