CVE-2016-3154 in SPIP
Summary
by MITRE
The encoder_contexte_ajax function in ecrire/inc/filtres.php in SPIP 2.x before 2.1.19, 3.0.x before 3.0.22, and 3.1.x before 3.1.1 allows remote attackers to conduct PHP object injection attacks and execute arbitrary PHP code via a crafted serialized object.
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Analysis
by VulDB Data Team • 02/05/2019
The vulnerability identified as CVE-2016-3154 resides within the encoder_contexte_ajax function located in the ecrire/inc/filtres.php file of the SPIP content management system. This critical security flaw affects multiple versions of SPIP including 2.x prior to 2.1.19, 3.0.x prior to 3.0.22, and 3.1.x prior to 3.1.1. The vulnerability stems from improper handling of serialized PHP objects within the application's filtering mechanism, creating a pathway for remote attackers to inject malicious PHP objects that can be subsequently executed. The flaw represents a classic PHP object injection vulnerability that allows attackers to manipulate the application's behavior through crafted input data.
The technical implementation of this vulnerability involves the improper sanitization of user-supplied input that gets processed through the encoder_contexte_ajax function. When SPIP receives serialized object data through its filtering system, it fails to properly validate or sanitize the serialized content before processing it. This oversight enables attackers to construct malicious serialized objects containing PHP code that gets executed when the object is unserialized. The vulnerability specifically targets the PHP serialization mechanism, where serialized objects can contain executable code that runs during the unserialization process, making it particularly dangerous for web applications that handle user input through serialization.
The operational impact of this vulnerability is severe and far-reaching for affected SPIP installations. Remote attackers can leverage this flaw to execute arbitrary PHP code on vulnerable systems, potentially leading to complete system compromise, data theft, or unauthorized access to sensitive information. The vulnerability enables attackers to perform actions such as creating backdoors, modifying content, accessing databases, or escalating privileges within the application environment. Given that SPIP is widely used for content management and web publishing, the potential for widespread exploitation exists across numerous websites and organizations that rely on this platform for their online presence.
This vulnerability aligns with CWE-502, which describes the weakness of deserializing untrusted data, and represents a direct violation of secure coding practices regarding object serialization and input validation. The attack vector follows patterns consistent with the MITRE ATT&CK framework's technique T1059.007 for "Command and Scripting Interpreter: PHP," where adversaries leverage PHP-specific vulnerabilities to execute malicious code. Organizations using affected SPIP versions face significant risk of compromise, as the vulnerability allows for persistent backdoor access and can be exploited without requiring authentication. The remediation process requires immediate patching of the affected SPIP versions to prevent exploitation, along with implementing proper input validation and output encoding measures to prevent similar vulnerabilities from occurring in the future.
The exploitation of this vulnerability demonstrates the critical importance of proper object serialization handling in web applications, particularly those processing user input through PHP's unserialize function. Security practitioners should implement comprehensive input validation, employ secure coding practices for serialization handling, and maintain up-to-date software versions to protect against such attacks. The vulnerability serves as a reminder of the persistent risks associated with legacy code handling and the necessity of thorough security testing for serialization-related functionality within web applications.