CVE-2012-0838 in Struts
Summary
by MITRE
Apache Struts 2 before 2.2.3.1 evaluates a string as an OGNL expression during the handling of a conversion error, which allows remote attackers to modify run-time data values, and consequently execute arbitrary code, via invalid input to a field.
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Analysis
by VulDB Data Team • 01/03/2025
The vulnerability identified as CVE-2012-0838 represents a critical remote code execution flaw within Apache Struts 2 framework versions prior to 2.2.3.1. This vulnerability resides in the framework's handling of conversion errors and demonstrates how seemingly minor processing logic can create significant security risks. The flaw specifically affects the OGNL (Object-Graph Navigation Language) expression evaluation mechanism that Apache Struts 2 employs for data binding and processing. When the framework encounters invalid input during conversion processes, it inadvertently evaluates user-supplied strings as OGNL expressions rather than treating them as simple data values.
The technical exploitation of this vulnerability occurs through carefully crafted malicious input that triggers the conversion error handling path. During normal operation, Apache Struts 2 processes form data and binds it to action properties using OGNL expressions for complex object manipulation. However, when invalid input is provided that cannot be properly converted, the framework's error handling routine attempts to evaluate the malformed input as an OGNL expression. This behavior creates an unintended code execution path where attacker-controlled strings are interpreted as executable code rather than data. The vulnerability is particularly dangerous because it allows remote attackers to inject arbitrary OGNL expressions that can manipulate runtime data values and ultimately execute arbitrary commands on the server.
From an operational perspective, this vulnerability has severe implications for web applications built on Apache Struts 2. The attack surface is broad as any application that accepts user input through forms or parameters and uses Struts 2's data binding capabilities could be compromised. Attackers can leverage this flaw to gain complete control over affected servers, potentially leading to data breaches, service disruption, and further lateral movement within network environments. The vulnerability maps directly to CWE-94, which describes "Improper Control of Generation of Code ('Code Injection')" and aligns with ATT&CK technique T1190 "Exploit Public-Facing Application" as it represents a remote exploitation vector through web application interfaces. The flaw also connects to ATT&CK technique T1059 "Command and Scripting Interpreter" since successful exploitation enables command execution on the target system.
Organizations affected by this vulnerability should prioritize immediate remediation through upgrading to Apache Struts 2 version 2.2.3.1 or later, which includes proper input validation and sanitization in the conversion error handling process. Additional mitigations include implementing web application firewalls to detect and block suspicious OGNL expression patterns, restricting network access to application servers, and conducting comprehensive security testing of all Struts 2 applications. The vulnerability demonstrates the critical importance of proper input validation and the principle of least privilege in web application security, where user-supplied data should never be directly evaluated as executable code without thorough sanitization and validation processes. Security teams should also consider implementing runtime monitoring to detect anomalous command execution patterns that may indicate exploitation attempts.