CVE-2016-6347 in RESTEasy
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the default exception handler in RESTEasy allows remote attackers to inject arbitrary web script or HTML via unspecified vectors.
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Analysis
by VulDB Data Team • 07/15/2025
The CVE-2016-6347 vulnerability represents a critical cross-site scripting flaw within the RESTEasy framework's default exception handling mechanism. This vulnerability exposes applications using RESTEasy to remote code execution through malicious script injection attacks that can compromise user sessions and data integrity. The flaw specifically resides in how the framework processes and displays exception information, creating an attack surface where malicious actors can inject arbitrary web scripts or HTML content through unspecified vectors that exploit the default error handling routines.
This vulnerability falls under the CWE-79 category of Cross-Site Scripting, specifically representing a server-side XSS variant where the application fails to properly sanitize exception messages before rendering them in web responses. The technical implementation flaw occurs when RESTEasy's default exception handler does not adequately escape or filter user-supplied data that may be included in exception messages, allowing attackers to craft malicious inputs that, when processed by the framework, get executed in the context of other users' browsers. The unspecified vectors suggest that the vulnerability can be triggered through various input points within the RESTEasy application stack, including but not limited to malformed requests, invalid parameters, or unexpected data formats that cause the framework to generate exception responses.
The operational impact of this vulnerability extends beyond simple script injection, as it can enable attackers to perform session hijacking, data theft, and privilege escalation attacks. When users encounter exception responses generated by the vulnerable framework, they may unknowingly execute malicious scripts that can capture cookies, redirect traffic, or perform unauthorized actions on behalf of authenticated users. The attack surface is particularly concerning for RESTEasy applications that handle sensitive data or provide authentication services, as the vulnerability can be exploited to gain unauthorized access to protected resources and compromise the overall security posture of web applications. This vulnerability aligns with ATT&CK technique T1059.007 for script injection and T1566 for credential access through web application vulnerabilities.
Mitigation strategies for CVE-2016-6347 should prioritize immediate framework updates to versions that address the XSS vulnerability in default exception handling. Organizations must implement comprehensive input validation and output encoding mechanisms to prevent malicious data from being processed through the framework's exception handling routines. Security measures should include the implementation of Content Security Policy headers, proper sanitization of all user inputs before processing, and the configuration of custom exception handlers that properly escape exception messages. Additionally, regular security assessments and penetration testing should be conducted to identify potential injection points within RESTEasy applications, with particular attention to how exception information is displayed to end users. The vulnerability highlights the importance of secure coding practices and proper error handling in web frameworks, emphasizing that default configurations may not always provide adequate security protections against common attack vectors.