CVE-2016-2162 in Struts
Summary
by MITRE
Apache Struts 2.x before 2.3.25 does not sanitize text in the Locale object constructed by I18NInterceptor, which might allow remote attackers to conduct cross-site scripting (XSS) attacks via unspecified vectors involving language display.
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Analysis
by VulDB Data Team • 02/03/2019
Apache Struts 2 versions prior to 2.3.25 contain a critical cross-site scripting vulnerability within the I18NInterceptor component that fails to properly sanitize locale information. This flaw exists in the way the framework processes internationalization parameters, specifically when constructing Locale objects that contain user-supplied data. The vulnerability stems from insufficient input validation and output encoding mechanisms within the internationalization subsystem, allowing malicious actors to inject malicious scripts through carefully crafted locale parameters. The issue manifests when the framework processes locale identifiers that contain HTML or script content, which are then rendered in the application's user interface without proper sanitization. This vulnerability falls under CWE-79 - Improper Neutralization of Input During Web Page Generation, and aligns with ATT&CK technique T1190 - Exploit Public-Facing Application, as it represents an attack vector through web application interfaces. The security implications extend beyond simple XSS, as attackers can leverage this weakness to steal session cookies, perform unauthorized actions on behalf of users, or redirect victims to malicious sites. The vulnerability affects the core internationalization functionality of Struts 2, making it particularly dangerous as it can be exploited through various user-facing interfaces that utilize locale parameters.
The technical exploitation of this vulnerability occurs when user input containing malicious script content is processed through the I18NInterceptor's locale handling mechanism. The interceptor creates Locale objects from potentially untrusted input without proper sanitization, allowing attackers to inject script tags or other malicious content that gets executed when the locale information is displayed to users. This flaw exists because the framework assumes that locale identifiers will contain only valid language and country codes, failing to validate or sanitize content that might contain HTML entities or script tags. The impact is particularly severe because locale parameters are often used in URL parameters, form submissions, or cookie values, providing multiple attack vectors for exploitation. The vulnerability demonstrates poor security practices in input validation and output encoding, as defined by CWE-502 - Deserialization of Untrusted Data, and represents a classic case of insecure data handling in web applications. Attackers can leverage this weakness to execute arbitrary JavaScript in the context of the victim's browser, potentially leading to complete session hijacking or data exfiltration.
The operational impact of CVE-2016-2162 extends far beyond simple XSS attacks, as it provides attackers with a foothold for more sophisticated exploitation techniques. Organizations running affected Struts 2 versions face significant risk of data breaches, as the vulnerability can be exploited to steal sensitive information, manipulate application behavior, or establish persistent access through session hijacking. The vulnerability affects the fundamental internationalization capabilities of web applications, meaning that any application utilizing Struts 2's I18N features is potentially vulnerable. This weakness can be particularly dangerous in enterprise environments where applications handle sensitive data, as attackers can use the XSS vector to escalate privileges or move laterally within the network. The attack surface is broad because locale parameters are commonly used in web applications for user experience personalization, making this vulnerability difficult to detect and prevent. Security professionals should note that this vulnerability aligns with ATT&CK technique T1068 - Exploitation for Privilege Escalation, as the initial XSS attack can be leveraged to gain higher-level access within the application environment. The widespread adoption of Apache Struts 2 in enterprise applications makes this vulnerability particularly concerning from a threat intelligence perspective, as it represents a common attack vector that has been exploited in numerous real-world incidents.
Organizations should immediately upgrade to Apache Struts 2 version 2.3.25 or later to remediate this vulnerability, as this release includes proper input sanitization and output encoding mechanisms for locale parameters. The upgrade process should include comprehensive testing to ensure that existing application functionality remains intact, particularly for applications that heavily utilize internationalization features. Security teams should implement additional mitigations such as web application firewalls that can detect and block malicious locale parameters, and deploy content security policies that prevent script execution in user-controllable contexts. Regular security assessments should include verification that all Struts 2 components are updated to supported versions, as this vulnerability has been actively exploited in the wild. Organizations should also implement proper input validation at multiple layers of their applications, ensuring that any user-supplied data is sanitized before being processed by framework components. The remediation process should include monitoring for exploitation attempts, as indicated by unusual locale parameter patterns in application logs, and establishing incident response procedures for potential XSS attacks. Security configurations should enforce strict output encoding for all user-controllable data, particularly in internationalization contexts, to prevent similar vulnerabilities from emerging in other components of the application stack.