CVE-2026-109219 in Mang Board Plugin
Summary
by MITRE • 10/16/2026
The Mang Board plugin for WordPress is vulnerable to Arbitrary File Upload in all versions up to, and including, 2.4.4 via the mbw_file_upload function. This is due to missing file extension validation on the attacker-supplied image_path parameter, whose basename-derived file name bypasses the extension allowlist applied only to the separate file_name parameter. This makes it possible for unauthenticated attackers to upload files that may be executable, which makes remote code execution possible. Exploitation requires the board to be configured to allow guest posts, which is the plugin's default mode; the required nonce is printed on every public board page, making it readable by any unauthenticated visitor without a WordPress login.
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Analysis
by VulDB Data Team • 10/16/2026
The Mang Board plugin for WordPress contains a critical security vulnerability affecting all versions up to and including 2.4.4. This flaw manifests as an arbitrary file upload issue within the mbw_file_upload function, allowing attackers to bypass standard security controls designed to prevent malicious code execution on web servers. The root cause of this vulnerability lies in inconsistent validation logic applied to different parameters during the file upload process. Specifically, while a separate parameter named file_name is subjected to strict extension allowlisting checks, the attacker-supplied image_path parameter lacks any corresponding file extension validation. This discrepancy creates a significant security gap that can be exploited by malicious actors to introduce executable scripts into the WordPress environment.
The technical mechanism of this exploit relies on how the plugin processes filenames derived from user input. When an unauthenticated visitor submits data through the mbw_file_upload function, the system extracts the basename from the image_path parameter and uses it as part of the final file name stored on the server. Because no extension validation is performed on this specific path component, attackers can craft requests that include executable extensions such as PHP or HTML with script tags in the image_path field. The allowlist check applied to the distinct file_name parameter fails to mitigate this risk because the system ultimately relies on the basename derived from the unvalidated image_path for storage decisions. This architectural flaw effectively renders the existing security controls ineffective against targeted attacks leveraging this specific code path.
The operational impact of this vulnerability is severe, as it directly facilitates remote code execution (RCE) on compromised WordPress sites. Once an attacker successfully uploads a malicious file with executable permissions or content interpreted by the web server, they gain the ability to run arbitrary commands within the context of the web application process. This level of access allows for complete compromise of the underlying system, including theft of sensitive data, installation of backdoors, and use of the compromised server as part of larger botnets. The severity is further amplified by the low barrier to entry required for exploitation. Unlike many other vulnerabilities that require authenticated administrative privileges, this flaw can be triggered by unauthenticated users who do not possess any valid WordPress login credentials.
Exploitation conditions are relatively permissive due to default configuration settings and accessible security tokens. The vulnerability requires only that the board is configured to allow guest posts, which corresponds to the plugin's default mode of operation. Furthermore, the nonce value required for CSRF protection is printed on every public board page. This design choice ensures that any unauthenticated visitor can easily retrieve the necessary token by viewing the source code or parsing the HTML response. Consequently, attackers do not need to perform complex reconnaissance or social engineering to obtain valid authentication tokens; they are publicly available and ready for immediate use in crafting exploit payloads.
From a classification perspective, this vulnerability aligns with CWE-434, which describes the unrestricted upload of files with dangerous types. It also maps closely to ATT&CK technique T1505.003, known as Web Shell: Cloud Accounts or general web shells, where attackers deploy malicious scripts to maintain persistent access and execute commands remotely. The lack of input validation on critical file path parameters represents a fundamental failure in secure coding practices that should have been addressed during the development lifecycle.
Mitigation strategies must address both immediate remediation and long-term security hygiene. Administrators running affected versions of the Mang Board plugin should upgrade to version 2.4.5 or later, where this validation gap has presumably been closed by enforcing extension checks on all relevant input parameters including image_path. In cases where upgrading is not immediately feasible, administrators can mitigate risk by disabling guest posting features if they are not essential for their specific use case. Additionally, implementing strict file upload restrictions at the web server level, such as configuring Apache or Nginx to deny execution of uploaded files in designated directories, provides a critical layer of defense-in-depth. Regular security audits and code reviews focusing on input validation consistency across all API endpoints can help prevent similar discrepancies from arising in future updates.