CVE-2013-10051 in InstantCMS
Summary
by MITRE • 08/02/2025
A remote PHP code execution vulnerability exists in InstantCMS version 1.6 and earlier due to unsafe use of eval() within the search view handler. Specifically, user-supplied input passed via the look parameter is concatenated into a PHP expression and executed without proper sanitation. A remote attacker can exploit this flaw by sending a crafted HTTP GET request with a base64-encoded payload in the Cmd header, resulting in arbitrary PHP code execution within the context of the web server.
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Analysis
by VulDB Data Team • 10/09/2025
This vulnerability represents a critical remote code execution flaw in InstantCMS version 1.6 and earlier systems that directly violates fundamental security principles of input validation and code execution control. The vulnerability stems from the unsafe implementation of the eval() function within the search view handler component, creating an attack surface where malicious input can be transformed into executable PHP code. The flaw specifically manifests when user-supplied data from the look parameter is improperly concatenated into PHP expressions without adequate sanitization or validation measures. This design flaw aligns with CWE-94, which categorizes improper control of generation of code, and demonstrates how the use of eval() functions creates inherent risks when combined with unsanitized user input. The vulnerability operates through a sophisticated exploitation technique where attackers craft HTTP GET requests containing base64-encoded payloads within the Cmd header, effectively bypassing normal input validation mechanisms and directly executing arbitrary PHP code on the target server.
The operational impact of this vulnerability extends far beyond simple code execution, as it provides attackers with complete control over the web server environment where InstantCMS operates. This remote code execution capability enables adversaries to perform a wide range of malicious activities including data exfiltration, privilege escalation, persistence establishment, and further network reconnaissance. The attack vector demonstrates the classic characteristics of a server-side request forgery vulnerability where user input directly influences the execution context, creating a persistent threat that can be exploited repeatedly without requiring user interaction. According to ATT&CK framework, this vulnerability maps to T1059.007 for PHP code execution and T1071.004 for application layer protocol usage, representing both execution and command and control communication patterns. The base64 encoding technique used in the exploitation process shows sophisticated attacker methodology designed to evade simple signature-based detection systems while maintaining the integrity of the malicious payload.
The security implications of this vulnerability extend to the broader context of web application security practices, particularly highlighting the dangers of using dynamic code execution functions in production environments. The flaw demonstrates how seemingly minor implementation decisions can create catastrophic security risks, as the eval() function becomes a gateway for arbitrary code execution when combined with unsanitized user input. Organizations running affected versions of InstantCMS face significant exposure to data breaches, system compromise, and potential lateral movement within their network infrastructure. The vulnerability's exploitation requires minimal technical expertise and can be automated, making it particularly dangerous in environments where multiple systems may be running vulnerable versions of the software. Mitigation strategies must include immediate patching of the affected software, implementation of web application firewalls to detect and block suspicious header patterns, and comprehensive input validation controls that prevent any user-supplied data from reaching code execution contexts. Additionally, security monitoring should be enhanced to detect unusual patterns in HTTP headers and base64 encoded content that may indicate exploitation attempts. The vulnerability serves as a prime example of why security-by-design principles are essential and why regular security assessments and code reviews should be mandatory practices in software development lifecycle processes.