CVE-2017-8912 in CMS Made Simple
Summary
by MITRE
** DISPUTED ** CMS Made Simple (CMSMS) 2.1.6 allows remote authenticated administrators to execute arbitrary PHP code via the code parameter to admin/editusertag.php, related to the CreateTagFunction and CallUserTag functions. NOTE: the vendor reportedly has stated this is "a feature, not a bug."
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Analysis
by VulDB Data Team • 07/23/2024
The vulnerability CVE-2017-8912 affects CMS Made Simple version 2.1.6 and represents a critical security flaw that enables authenticated administrators to execute arbitrary PHP code through a specially crafted input parameter. This issue resides within the admin/editusertag.php file where the code parameter is processed through the CreateTagFunction and CallUserTag functions. The vulnerability is particularly concerning because it operates within the administrative context, meaning that an attacker who has already gained administrative privileges can leverage this flaw to escalate their capabilities and potentially compromise the entire system.
The technical implementation of this vulnerability stems from improper input validation and sanitization within the user tag creation functionality of CMS Made Simple. When administrators create or modify user-defined tags, the system fails to adequately sanitize the code parameter, allowing malicious code injection. This flaw aligns with CWE-94, which describes "Improper Control of Generation of Code ('Code Injection')" and specifically relates to the improper handling of user-supplied input in PHP applications. The vulnerability exists because the system does not properly validate or escape the input before executing it as PHP code, creating a direct path for code execution.
From an operational perspective, this vulnerability presents a significant risk to organizations relying on CMS Made Simple as their content management platform. The fact that this is a remote authenticated vulnerability means that an attacker with valid administrative credentials can execute arbitrary commands on the server. This capability can be exploited to establish persistent backdoors, exfiltrate sensitive data, modify website content, or even use the compromised system as a pivot point to attack other systems within the network. The impact extends beyond simple code execution as it can lead to full system compromise and data breaches, particularly when administrative accounts are compromised through other means such as credential theft or social engineering attacks.
The vendor's response that this is "a feature, not a bug" reflects a controversial stance that highlights the complexity of defining security vulnerabilities in web applications. While the functionality may have been intended to allow advanced users to create custom tags with PHP code, the lack of proper input validation and sanitization transforms this legitimate feature into a security risk. This vulnerability demonstrates the importance of implementing proper security controls even for features that appear to be intentionally designed for advanced functionality. Organizations should consider implementing additional security measures such as input validation, output encoding, and privilege separation to mitigate the risk of such vulnerabilities. The incident also underscores the need for comprehensive security testing, including security code reviews and penetration testing, to identify potential misuse of legitimate application features.
The attack vector for this vulnerability involves an authenticated administrative session where an attacker can manipulate the code parameter in the admin/editusertag.php endpoint. This aligns with ATT&CK technique T1059.007, which describes "Command and Scripting Interpreter: PowerShell" but can be adapted to represent PHP code execution through legitimate administrative interfaces. The vulnerability essentially creates a backdoor within the application's intended functionality, making it particularly dangerous as it can bypass traditional security controls that might not monitor administrative activities. Organizations should implement monitoring and logging of administrative activities, especially when dealing with code execution capabilities, to detect potential exploitation attempts. The remediation approach should include immediate patching of the affected CMS Made Simple version, implementation of proper input validation, and consideration of privilege-based access controls to limit the scope of potential exploitation.