CVE-2016-4000 in Rapid Planning
Summary
by MITRE
Jython before 2.7.1rc1 allows attackers to execute arbitrary code via a crafted serialized PyFunction object.
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Analysis
by VulDB Data Team • 05/17/2025
The vulnerability identified as CVE-2016-4000 represents a critical remote code execution flaw within the Jython runtime environment. This security issue affects Jython versions prior to 2.7.1rc1 and stems from insufficient validation of serialized objects during deserialization processes. The vulnerability specifically targets PyFunction objects which are Python function representations that can be serialized and transmitted across network boundaries. When a maliciously crafted serialized PyFunction object is processed by an affected Jython system, it can trigger arbitrary code execution on the target machine, bypassing normal security boundaries and potentially allowing full system compromise.
The technical root cause of this vulnerability lies in the unsafe deserialization mechanism within Jython's object handling code. When Jython processes serialized Python objects, it does not properly validate the integrity or authenticity of these objects before executing them. This design flaw creates an attack surface where untrusted serialized data can be manipulated to execute malicious payloads. The vulnerability is particularly dangerous because it can be exploited through network-based attacks where attackers send specially crafted serialized objects to vulnerable Jython applications. The flaw operates at the core of Jython's serialization framework, making it difficult to mitigate without addressing the underlying deserialization logic.
The operational impact of CVE-2016-4000 extends beyond simple code execution to encompass complete system compromise and data breaches. Attackers exploiting this vulnerability can gain unauthorized access to sensitive systems, potentially leading to data exfiltration, privilege escalation, and persistent backdoor installation. The vulnerability affects any application or service that relies on Jython for scripting capabilities and processes serialized Python objects from untrusted sources. Organizations using Jython in web applications, enterprise systems, or any environment where external data processing occurs face significant risk. The attack vector is particularly concerning because it can be triggered remotely without requiring authentication, making it an attractive target for automated exploitation campaigns.
Mitigation strategies for CVE-2016-4000 primarily focus on immediate version upgrades to Jython 2.7.1rc1 or later releases where the vulnerability has been addressed. Organizations should implement comprehensive patch management procedures to ensure all affected systems receive updates promptly. Additional defensive measures include restricting network access to Jython applications, implementing strict input validation for serialized data, and employing network segmentation to limit the potential impact of successful exploits. The vulnerability aligns with CWE-502 which classifies unsafe deserialization as a significant security weakness, and it maps to ATT&CK technique T1059.007 for script-based execution. Security teams should also consider implementing application whitelisting policies and monitoring for unusual deserialization activities that might indicate exploitation attempts.