CVE-2016-3087 in Struts
Summary
by MITRE
Apache Struts 2.3.19 to 2.3.20.2, 2.3.21 to 2.3.24.1, and 2.3.25 to 2.3.28, when Dynamic Method Invocation is enabled, allow remote attackers to execute arbitrary code via vectors related to an ! (exclamation mark) operator to the REST Plugin.
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Analysis
by VulDB Data Team • 01/19/2025
Apache Struts 2 represents a widely adopted web application framework for building enterprise Java applications, with numerous organizations relying on its capabilities for developing dynamic web content and services. The vulnerability described in CVE-2016-3087 specifically targets versions of this framework that are susceptible to remote code execution when Dynamic Method Invocation is enabled within the REST Plugin component. This flaw operates through a critical design oversight that permits attackers to manipulate input parameters in ways that bypass normal security controls and execute malicious code on the target server. The vulnerability manifests when the framework processes requests containing specific parameter sequences that include the exclamation mark operator, which serves as a delimiter for method invocation in the framework's internal processing mechanisms. The affected versions span multiple release cycles, indicating that this vulnerability persisted across several iterations of the software, potentially affecting a substantial number of deployments. The presence of Dynamic Method Invocation as an enabled feature creates an attack surface where user-supplied input can directly influence the framework's method resolution process, allowing for unauthorized execution of arbitrary code with the privileges of the web application. This vulnerability directly maps to CWE-94, which describes "Improper Control of Generation of Code" and aligns with ATT&CK technique T1059.007 for "Command and Scripting Interpreter: PowerShell" as it enables attackers to execute system commands through the application layer.
The technical exploitation of this vulnerability occurs when a malicious actor crafts a request that includes specially formatted parameters containing the exclamation mark operator, which then gets processed by the REST Plugin's parameter handling mechanism. The framework's insufficient validation of input parameters allows the attacker to inject method calls that bypass the intended security boundaries, effectively enabling remote code execution capabilities. The attack vector specifically leverages the REST Plugin's ability to interpret method names from URL parameters, where the exclamation mark serves as a delimiter between the action name and the method to be invoked. This design flaw allows attackers to manipulate the method resolution process by injecting additional method calls that execute arbitrary code on the target system. The vulnerability's impact extends beyond simple code execution, as it can potentially provide attackers with complete system compromise capabilities, including the ability to access sensitive data, establish persistence mechanisms, and escalate privileges within the application environment. The exploitation requires only a single request to be sent to the vulnerable application, making it particularly dangerous as it can be executed through automated tools and scripts without requiring complex multi-stage attacks.
Organizations utilizing affected Apache Struts versions face significant operational risks, as this vulnerability can be exploited by threat actors without requiring authentication or specialized knowledge of the underlying system architecture. The widespread adoption of Apache Struts across enterprise environments means that numerous applications could be simultaneously vulnerable, creating a large attack surface for potential exploitation. Security teams must consider the implications of this vulnerability in their incident response planning, as successful exploitation can lead to data breaches, service disruption, and regulatory compliance violations. The vulnerability's persistence across multiple versions suggests that organizations may have been exposed for extended periods without detection, potentially allowing attackers to establish long-term presence within affected networks. Mitigation efforts should focus on immediate patching of affected systems, disabling Dynamic Method Invocation where possible, and implementing network-level controls to prevent access to vulnerable endpoints. Organizations should also consider implementing web application firewalls and monitoring for suspicious parameter patterns that could indicate exploitation attempts.
The remediation approach for this vulnerability requires immediate application of security patches provided by Apache Software Foundation, as these updates contain fixes for the parameter validation issues that enable the attack. System administrators should also consider implementing configuration changes that disable Dynamic Method Invocation in the REST Plugin when it is not required for application functionality. Additionally, organizations should conduct comprehensive vulnerability assessments to identify all instances of affected Apache Struts versions within their infrastructure, as this vulnerability may be present in multiple applications and services. Security monitoring should be enhanced to detect unusual parameter patterns and request behaviors that could indicate exploitation attempts, while network segmentation and access controls should be reviewed to limit the potential impact of successful exploitation. The vulnerability demonstrates the critical importance of maintaining up-to-date software components and implementing proper input validation controls in web applications, as these measures form the foundation of effective security posture against such remote code execution threats.