CVE-2008-6504 in XWork
Summary
by MITRE
ParametersInterceptor in OpenSymphony XWork 2.0.x before 2.0.6 and 2.1.x before 2.1.2, as used in Apache Struts and other products, does not properly restrict # (pound sign) references to context objects, which allows remote attackers to execute Object-Graph Navigation Language (OGNL) statements and modify server-side context objects, as demonstrated by use of a \u0023 representation for the # character.
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Analysis
by VulDB Data Team • 02/13/2025
The vulnerability identified as CVE-2008-6504 represents a critical security flaw in the ParametersInterceptor component of OpenSymphony XWork, a core framework component that serves as the foundation for Apache Struts applications. This vulnerability affects versions prior to 2.0.6 for the 2.0.x series and 2.1.2 for the 2.1.x series, creating a significant attack surface for malicious actors targeting web applications built on these frameworks. The flaw specifically resides in how the system handles parameter processing and context object restrictions, enabling attackers to bypass intended security controls through carefully crafted input sequences.
The technical implementation of this vulnerability stems from improper sanitization of the pound sign character within parameter values. The ParametersInterceptor, which is responsible for managing parameter binding and context object access in XWork-based applications, fails to adequately restrict the interpretation of the # character in parameter values. This oversight allows attackers to inject OGNL (Object-Graph Navigation Language) expressions that can execute arbitrary code on the server. The vulnerability becomes particularly dangerous when attackers utilize the Unicode escape sequence \u0023 to represent the # character, effectively circumventing standard input validation mechanisms that might be looking for literal pound signs in parameter values.
The operational impact of this vulnerability is severe and multifaceted, as it enables remote code execution capabilities that can compromise entire server environments. Attackers can leverage this flaw to manipulate server-side context objects, execute arbitrary OGNL expressions, and potentially gain full control over the affected application server. The ability to modify context objects means that attackers can access sensitive application data, modify application behavior, and potentially escalate privileges within the server environment. This vulnerability directly maps to CWE-94, which describes the weakness of "Improper Control of Generation of Code" and falls under the broader category of code injection vulnerabilities that can lead to arbitrary code execution.
The exploitation of this vulnerability aligns with several tactics described in the MITRE ATT&CK framework, particularly those related to command and control operations and privilege escalation. Attackers can use this vulnerability to establish persistent access to target systems, execute malicious code, and potentially move laterally within network environments. The vulnerability's impact extends beyond simple code execution to include data manipulation and confidentiality breaches, as context objects often contain sensitive information about application state and user data.
Organizations affected by this vulnerability should prioritize immediate remediation through patching to versions 2.0.6 or 2.1.2 and later, which contain the necessary fixes to properly restrict pound sign references in parameter processing. Additional mitigations include implementing comprehensive input validation at multiple layers of the application architecture, utilizing web application firewalls to detect and block suspicious parameter sequences, and conducting thorough security reviews of parameter handling code within affected applications. The fix implemented in the patched versions ensures proper sanitization of the # character and prevents OGNL expression evaluation in contexts where such execution should be restricted, thereby addressing the root cause of the vulnerability and protecting against the associated security risks.