CVE-2020-35942 in NextGEN Gallery
Summary
by MITRE • 02/10/2021
A Cross-Site Request Forgery (CSRF) issue in the NextGEN Gallery plugin before 3.5.0 for WordPress allows File Upload and Local File Inclusion via settings modification, leading to Remote Code Execution and XSS. (It is possible to bypass CSRF protection by simply not including a nonce parameter.)
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Analysis
by VulDB Data Team • 02/27/2021
The vulnerability identified as CVE-2020-35942 represents a critical cross-site request forgery flaw within the NextGEN Gallery plugin for WordPress systems. This security weakness affects versions prior to 3.5.0 and stems from inadequate protection mechanisms that allow unauthorized users to manipulate plugin settings through malicious requests. The vulnerability specifically exploits the absence of proper nonce validation, enabling attackers to bypass CSRF protection entirely by simply omitting the required security token parameter. This fundamental flaw in the authentication flow creates a pathway for attackers to perform unauthorized operations with elevated privileges.
The technical implementation of this vulnerability resides in the plugin's handling of administrative requests and form submissions. When users access the NextGEN Gallery settings interface, the system should validate that each request originates from a legitimate administrative session through the use of cryptographic nonce tokens. However, the vulnerable code fails to enforce this validation consistently, particularly during file upload and local file inclusion operations. The absence of proper nonce verification creates a condition where attackers can craft malicious requests that appear to come from authenticated administrators, effectively allowing them to modify plugin configurations without proper authorization. This flaw aligns with CWE-352, which specifically addresses cross-site request forgery vulnerabilities where insufficient anti-CSRF measures are implemented in web applications.
The operational impact of this vulnerability extends far beyond simple privilege escalation, creating multiple attack vectors that can lead to complete system compromise. Through the bypassed CSRF protection, attackers can execute file upload operations that may allow them to place malicious scripts on the web server. The combination of file upload capabilities with local file inclusion vulnerabilities creates a powerful exploitation chain that can result in remote code execution on the target system. Additionally, the vulnerability enables cross-site scripting attacks that can be used to steal session cookies, redirect users to malicious sites, or perform further attacks against the authenticated user. The attack surface is significantly expanded because the vulnerability affects not just the plugin's administrative interface but also its underlying file handling mechanisms.
The security implications of this vulnerability are particularly severe in WordPress environments where NextGEN Gallery is installed, as it provides attackers with a potential foothold for broader system compromise. The ability to perform remote code execution through this vector means that attackers can potentially gain complete control over the web server hosting the WordPress installation. Furthermore, the combination of XSS capabilities with the file upload functionality creates opportunities for persistent attacks that can maintain access even after initial exploitation. This vulnerability demonstrates the critical importance of proper input validation and authentication mechanisms in web applications, particularly those handling sensitive administrative operations.
Mitigation strategies for CVE-2020-35942 require immediate action to upgrade the NextGEN Gallery plugin to version 3.5.0 or later, which contains the necessary fixes for the CSRF protection mechanisms. Organizations should also implement additional security measures including regular security audits of installed plugins, monitoring for unauthorized administrative changes, and implementing web application firewalls to detect and block suspicious requests. The fix addresses the core issue by properly enforcing nonce validation for all administrative operations, ensuring that each request contains valid authentication tokens before processing. Security practitioners should also consider implementing additional layers of protection such as role-based access controls and regular security scanning to prevent similar vulnerabilities from being exploited in other components of the WordPress ecosystem. This vulnerability serves as a reminder of the critical need for proper CSRF protection implementation and the potential consequences of inadequate authentication mechanisms in web applications.