CVE-2016-5727 in Simple Machines Forum
Summary
by MITRE
LogInOut.php in Simple Machines Forum (SMF) 2.1 allows remote attackers to conduct PHP object injection attacks and execute arbitrary PHP code via vectors related to variables derived from user input in a foreach loop.
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Analysis
by VulDB Data Team • 11/12/2022
The vulnerability identified as CVE-2016-5727 affects Simple Machines Forum version 2.1 and represents a critical PHP object injection flaw that enables remote attackers to execute arbitrary code on affected systems. This vulnerability exists within the LogInOut.php script which processes user authentication and logout operations, making it a prime target for exploitation in web application attacks. The flaw stems from improper handling of user-supplied data within a foreach loop structure, creating a pathway for attackers to inject malicious PHP objects that can be serialized and subsequently deserialized by the application.
The technical implementation of this vulnerability involves the manipulation of variables that are processed through a foreach loop in the LogInOut.php file. When user input flows directly into this loop without proper sanitization or validation, attackers can craft malicious payloads that, when processed, trigger PHP object deserialization. This process allows attackers to inject serialized objects containing malicious code that executes within the context of the web server. The vulnerability is categorized under CWE-502 as it involves deserialization of untrusted data, specifically PHP objects that contain executable code rather than simple data structures. The attack vector is particularly dangerous because it leverages the legitimate foreach loop functionality to execute code, making detection more challenging.
The operational impact of CVE-2016-5727 extends beyond simple code execution, as it provides attackers with full control over the affected web server. Successful exploitation can lead to complete system compromise, allowing attackers to install backdoors, exfiltrate sensitive data, modify forum content, or use the compromised server for further attacks. The vulnerability affects not just individual users but entire forum installations, potentially exposing thousands of users' personal information and credentials. Organizations running SMF 2.1 are particularly at risk as the vulnerability can be exploited through simple HTTP requests without requiring authentication, making it an attractive target for automated attacks. The attack can be classified under ATT&CK technique T1059.007 for PHP code execution, and T1078 for valid accounts usage, as attackers can leverage the compromised system to establish persistence and move laterally within networks.
Mitigation strategies for CVE-2016-5727 require immediate patching of the SMF 2.1 installation with the official security update provided by Simple Machines. Organizations should also implement input validation and sanitization measures to prevent user-supplied data from being processed in unsafe contexts. Network-level protections such as web application firewalls can help detect and block exploitation attempts, while monitoring for unusual PHP execution patterns can aid in identifying potential compromises. Regular security audits of web applications should include verification of proper object serialization handling and comprehensive testing of user input processing. The vulnerability demonstrates the importance of following secure coding practices as outlined in OWASP Top Ten, particularly the prevention of deserialization vulnerabilities and proper input validation techniques that should be implemented throughout the application lifecycle.