CVE-2019-9056 in CMS Made Simple
Summary
by MITRE
An issue was discovered in CMS Made Simple 2.2.8. In the module FrontEndUsers (in the file class.FrontEndUsersManipulate.php or class.FrontEndUsersManipulator.php), it is possible to reach an unserialize call with an untrusted __FEU__ cookie, and achieve authenticated object injection.
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Analysis
by VulDB Data Team • 05/29/2020
The vulnerability identified as CVE-2019-9056 represents a critical security flaw in CMS Made Simple version 2.2.8 that stems from improper input validation within the FrontEndUsers module. This issue specifically manifests in the class.FrontEndUsersManipulate.php or class.FrontEndUsersManipulator.php files where user-controlled data from the _FEU_ cookie is processed without adequate sanitization. The vulnerability is classified as a deserialization flaw that allows authenticated attackers to inject malicious objects into the application's memory space, creating a potential pathway for arbitrary code execution.
The technical exploitation of this vulnerability occurs through the unserialize() function call which processes data from the untrusted _FEU_ cookie. When an authenticated user visits a maliciously crafted page, the application's deserialization mechanism attempts to reconstruct objects from the serialized cookie data without proper validation. This creates a scenario where attackers can craft specially formatted cookie values that, when deserialized, execute arbitrary PHP code within the context of the web application. The vulnerability is particularly dangerous because it requires only authenticated access, meaning that an attacker with valid user credentials can leverage this flaw to escalate their privileges or compromise the entire application environment.
The operational impact of CVE-2019-9056 extends beyond simple code execution as it provides attackers with the capability to manipulate the application's behavior in potentially devastating ways. Successful exploitation could allow attackers to gain persistent access to the web server, extract sensitive user data, modify content, or even establish backdoors for future access. The vulnerability affects the core functionality of the FrontEndUsers module which is commonly used for managing user accounts and access control, making the potential damage significant for organizations relying on this CMS platform. This flaw directly maps to CWE-502 which describes "Deserialization of Untrusted Data" and aligns with ATT&CK technique T1203 which covers "Exploitation for Client Execution" and T1078 which addresses "Valid Accounts" as the vulnerability requires authenticated access to be exploited.
Organizations should implement immediate mitigations including upgrading to CMS Made Simple version 2.2.9 or later where this vulnerability has been patched, disabling the vulnerable FrontEndUsers module if it is not essential for operations, and implementing strict input validation for all cookie data. Network-based mitigations such as web application firewalls can help detect and block malicious cookie values, while application-level protections should enforce proper serialization and deserialization practices. Security monitoring should focus on detecting unusual cookie patterns and unauthorized access attempts to the FrontEndUsers module. Additionally, administrators should conduct comprehensive security audits of all installed modules and ensure that proper access controls are in place to minimize the potential impact of such vulnerabilities. The vulnerability underscores the importance of secure coding practices and proper input validation in preventing object injection attacks that can lead to complete system compromise.