CVE-2017-9805 in Struts
Summary
by MITRE
The REST Plugin in Apache Struts 2.1.1 through 2.3.x before 2.3.34 and 2.5.x before 2.5.13 uses an XStreamHandler with an instance of XStream for deserialization without any type filtering, which can lead to Remote Code Execution when deserializing XML payloads.
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Analysis
by VulDB Data Team • 12/25/2024
The vulnerability identified as CVE-2017-9805 represents a critical remote code execution flaw within Apache Struts 2 frameworks that has significant implications for web application security. This vulnerability specifically affects the REST Plugin component of Apache Struts, which is widely used for building web services and applications that handle XML data. The affected versions span from 2.1.1 through 2.3.x before 2.3.34 and 2.5.x before 2.5.13, indicating a substantial attack surface across multiple release lines of the framework.
The technical root cause of this vulnerability lies in the improper implementation of XStream deserialization within the XStreamHandler class. XStream is a popular Java library for serializing and deserializing objects to and from XML format. When the REST Plugin processes XML payloads containing serialized objects, it creates an XStream instance without applying any type filtering mechanisms. This design flaw allows attackers to craft malicious XML payloads that, when processed by the vulnerable application, can execute arbitrary code on the server. The absence of type filtering means that XStream will attempt to deserialize any class referenced in the XML payload, regardless of whether it's safe or malicious.
The operational impact of this vulnerability is severe and far-reaching, as it enables attackers to achieve complete system compromise without requiring authentication or specific privileges. According to the CWE (Common Weakness Enumeration) classification, this vulnerability maps to CWE-502 which describes "Deserialization of Untrusted Data" - a well-known weakness that has been exploited in numerous high-profile attacks. The ATT&CK framework categorizes this as a Remote Code Execution technique where adversaries leverage deserialization vulnerabilities to execute malicious code on target systems. Attackers can leverage this vulnerability to establish persistent backdoors, exfiltrate sensitive data, or use the compromised system as a launchpad for further attacks within the network infrastructure.
The exploitation process typically involves crafting a malicious XML payload that references dangerous Java classes such as java.lang.Runtime or other system classes that can execute commands. When the vulnerable application processes this XML through the XStreamHandler, the deserialization process triggers the execution of arbitrary code on the server. This vulnerability is particularly dangerous because it can be exploited through web requests that appear legitimate, making detection and prevention challenging. Organizations using affected versions of Apache Struts are at significant risk, as this vulnerability has been actively exploited in the wild, with security researchers documenting successful exploitation attempts against various web applications.
Mitigation strategies for CVE-2017-9805 primarily focus on immediate patching of affected systems, as the most effective solution involves upgrading to Apache Struts versions 2.3.34 or 2.5.13 and later. Organizations should also implement network-level defenses including firewall rules that restrict access to XML endpoints and web application firewalls that can detect and block suspicious XML payloads. Additionally, application-level safeguards such as implementing proper input validation, disabling unnecessary deserialization functionality, and using type filtering mechanisms can provide additional layers of protection. Security teams should conduct comprehensive vulnerability assessments to identify all instances of affected Apache Struts installations within their infrastructure and ensure that proper monitoring and alerting mechanisms are in place to detect potential exploitation attempts. The vulnerability serves as a stark reminder of the importance of secure coding practices and the critical need for proper input validation and sanitization in web applications that handle external data processing.