CVE-2017-3202 in Flamingo amf-serializer
Summary
by MITRE
The Java implementation of AMF3 deserializers used in Flamingo amf-serializer by Exadel, version 2.2.0, may allow instantiation of arbitrary classes via their public parameter-less constructor and subsequently call arbitrary Java Beans setter methods. The ability to exploit this vulnerability depends on the availability of classes in the class path that make use of deserialization. A remote attacker with the ability to spoof or control information may be able to send serialized Java objects with pre-set properties that result in arbitrary code execution when deserialized.
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Analysis
by VulDB Data Team • 12/26/2024
The vulnerability identified as CVE-2017-3202 represents a critical deserialization flaw within the Java implementation of AMF3 deserializers used in Flamingo amf-serializer version 2.2.0 by Exadel. This issue stems from the insecure deserialization practices that allow attackers to manipulate serialized data streams to instantiate arbitrary Java classes through their public parameter-less constructors. The vulnerability operates at the intersection of several security concerns including insecure deserialization patterns and Java serialization abuse, creating a pathway for remote code execution when exploited properly.
The technical flaw manifests in the AMF3 deserialization process where the system fails to properly validate or restrict the types of classes that can be instantiated during deserialization. When deserializing AMF3 formatted data, the vulnerable component accepts serialized objects that contain class references and attempts to instantiate these classes using their default constructors. This behavior creates an attack surface where maliciously crafted serialized data can trigger instantiation of classes from the application's classpath, potentially including system classes that could lead to arbitrary code execution. The vulnerability is particularly dangerous because it leverages the JavaBeans property mechanism, allowing attackers to call setter methods on instantiated objects, thereby enabling complex attack payloads.
The operational impact of this vulnerability extends beyond simple remote code execution, as it can be exploited to perform various malicious activities including privilege escalation, data exfiltration, and system compromise. Attackers can construct serialized objects that, when processed by the vulnerable deserializer, trigger the instantiation of classes that perform harmful operations such as executing system commands, establishing reverse shells, or accessing sensitive data. The attack requires a remote attacker who can control or spoof the information being sent to the vulnerable system, making it particularly concerning for web applications and services that accept serialized data from external sources. This vulnerability aligns with CWE-502 which specifically addresses deserialization of untrusted data, and can be mapped to ATT&CK technique T1059.007 for command and script interpreter execution through Java deserialization.
The exploitation of this vulnerability depends heavily on the availability of suitable classes within the application's classpath that can be leveraged for malicious purposes. This typically involves classes that have dangerous methods or that can be used to perform system operations when instantiated and their properties set. The attack vector can be particularly insidious because it can be carried out through standard network communication channels without requiring special privileges or complex attack chains. Organizations using Flamingo amf-serializer version 2.2.0 should consider this vulnerability as a high-priority concern, especially in environments where serialized data is processed from untrusted sources. The recommended mitigations include upgrading to a patched version of the library, implementing proper input validation and sanitization, using secure deserialization practices, and employing additional security controls such as application firewalls and runtime monitoring to detect and prevent exploitation attempts.