CVE-2026-73996 in Masteriyo Plugin
Summary
by MITRE • 08/18/2026
Unauthenticated Arbitrary File Upload in Masteriyo - LMS <= 2.3.2 versions.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 08/18/2026
The vulnerability identified as an unauthenticated arbitrary file upload flaw within Masteriyo Learning Management System versions prior to or equal to 2.3.2 represents a critical security deficiency that allows remote attackers to execute code on the target server without any form of authentication. This type of vulnerability is particularly severe because it bypasses the fundamental access control mechanisms designed to protect administrative functions and sensitive data storage areas. The core technical flaw lies in the application's handling of file uploads, specifically within endpoints or API routes intended for legitimate user interactions such as uploading course materials, profile pictures, or other media assets. In these vulnerable versions, the server fails to adequately validate the source of the request, allowing an unauthenticated actor to interact with upload functionality that should be restricted to logged-in users or administrators. Furthermore, the validation logic regarding file types and extensions is insufficient, often relying on client-side checks or easily spoofable headers rather than robust server-side MIME type verification and content inspection. This lack of rigorous sanitization enables attackers to bypass extension whitelists by manipulating request parameters or exploiting parsing ambiguities in how the web server interprets uploaded files.
From a technical perspective, this vulnerability aligns with CWE-434, which describes an unrestricted upload of file with dangerous type. The attacker can craft a malicious HTTP POST request containing a script payload disguised as a legitimate document image or archive. Because the application does not enforce strict authentication checks on these specific endpoints, the server processes and stores the uploaded content in a publicly accessible directory. Once stored, the web server interprets files with executable extensions such as PHP, ASPX, or JSP as code rather than static data. This leads directly to CWE-94, Improper Control of Generation of Code (Code Injection), where the injected script is executed within the context of the web application process. The operational impact of this flaw is catastrophic for system integrity and confidentiality. An attacker can achieve Remote Code Execution by uploading a web shell or backdoor script. This grants them full control over the underlying operating system, depending on the privileges under which the web server runs. With such access, attackers can exfiltrate sensitive student data, modify course content to inject malicious links, install additional malware for persistent access, and pivot into other systems within the internal network infrastructure.
This attack vector is frequently utilized in automated scanning campaigns targeting popular open-source learning management platforms due to its high success rate against misconfigured or outdated installations. The exploitation process typically involves identifying the specific upload endpoint through directory enumeration or analyzing JavaScript files that define API routes. Once identified, the attacker constructs a multipart form-data request with appropriate headers but omits any session cookies or authentication tokens if they are not strictly enforced by the server-side logic for that particular route. After successful upload, the attacker accesses the file via its known URL path and triggers execution through various methods such as direct browser access or using command-line tools like curl to send specific payloads that interact with system commands. The presence of this vulnerability indicates a significant lapse in secure coding practices during the development phase, particularly regarding input validation and authentication middleware application across all functional modules.
Mitigation strategies must focus on immediate remediation through software updates and architectural hardening. The primary defense is upgrading Masteriyo to version 2.3.3 or later where this issue has been patched by enforcing strict authentication requirements for all file upload operations. For systems that cannot be immediately updated, temporary mitigations include configuring the web server to disable script execution in directories designated for user uploads. This can be achieved through specific configuration directives such as setting ExecCGI off in Apache or using location blocks with deny all rules in Nginx for executable extensions within those paths. Additionally implementing a Web Application Firewall rule set that detects and blocks common file upload patterns associated with web shells can provide an additional layer of defense. It is also critical to ensure that the application employs strict allow-lists for permitted file types, verifies MIME types against actual file content using libraries like libmagic, and renames uploaded files to random strings to prevent predictable path traversal or direct access by attackers who may not know the exact filename generated by the server. Regular security audits and penetration testing should be conducted to identify similar weaknesses in other modules of the learning management system.