CVE-2018-11331 in Pluck
Summary
by MITRE
An issue was discovered in Pluck before 4.7.6. Remote PHP code execution is possible because the set of disallowed filetypes for uploads in missing some applicable ones such as .phtml and .htaccess.
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Analysis
by VulDB Data Team • 03/14/2023
The vulnerability identified as CVE-2018-11331 represents a critical security flaw in the Pluck content management system prior to version 4.7.6. This issue stems from an inadequate file type validation mechanism that fails to properly restrict uploadable file extensions, creating a pathway for remote code execution attacks. The flaw specifically manifests in the application's upload functionality where certain file extensions that could be exploited for malicious purposes are not properly blacklisted, allowing attackers to bypass security controls and potentially execute arbitrary PHP code on the target server.
This vulnerability directly maps to CWE-434, which describes insecure file upload vulnerabilities where applications fail to properly validate file types and extensions. The technical implementation flaw lies in the incomplete blacklist of file extensions within the upload validation logic, specifically omitting critical extensions such as .phtml and .htaccess from the list of forbidden file types. The .phtml extension is particularly dangerous as it represents PHP Hypertext Preprocessor files that can execute server-side code, while .htaccess files can be used to modify server configuration and potentially enable malicious behaviors when uploaded to web servers. The incomplete validation creates a false sense of security where administrators believe certain file types are blocked, but attackers can exploit the gap to upload malicious files.
The operational impact of this vulnerability is severe and multifaceted, as it enables attackers to achieve remote code execution capabilities that can lead to complete system compromise. An attacker who successfully exploits this vulnerability can upload malicious files that execute arbitrary code on the web server, potentially leading to data theft, system infiltration, and further lateral movement within the network. This vulnerability aligns with ATT&CK technique T1190, which covers exploiting vulnerabilities in web applications, and T1059, which covers command and script injection. The attack surface is particularly concerning because it allows for persistent access through the upload of web shells or other malicious payloads that can be used for extended periods without detection.
The mitigation strategy for this vulnerability requires immediate application of the vendor-provided patch to version 4.7.6 or later, which properly addresses the incomplete file type validation. Organizations should also implement additional defensive measures including comprehensive file type validation that employs both allowlists and denylists, proper file extension checking, and content-type verification. Network-level protections such as web application firewalls should be configured to monitor and block suspicious file upload attempts. Security teams should conduct thorough audits of all file upload functionalities across their systems, ensuring that all potentially dangerous file extensions are properly restricted and that proper file content validation is implemented. Additionally, implementing proper access controls and monitoring for unusual file upload activities can help detect potential exploitation attempts before they succeed.