CVE-2026-88419 in WuzhiCMS
Summary
by MITRE • 09/22/2026
An unrestricted upload of files with a dangerous type in the thumbnail-upload endpoint (/index.php?m=member&f=article&v=thumbUpload) of WuzhiCMS 5.0.0 allows an authenticated low-privileged member to upload a crafted .php file and execute arbitrary PHP code on the server, because the stored file extension is taken verbatim from the client-supplied filename with no extension allowlist or content validation and the file is written to the web-accessible uploadfile/ directory, from which the web server executes PHP.
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Analysis
by VulDB Data Team • 09/22/2026
The vulnerability identified in WuzhiCMS version 5.0.0 represents a critical security flaw rooted in improper input validation within the thumbnail-upload endpoint located at /index.php?m=member&f=article&v=thumbUpload. This specific function is designed to handle image uploads for article thumbnails, yet it fails to enforce strict constraints on file types or content verification. The core technical deficiency lies in how the application processes the filename provided by the client during the upload process. Instead of validating the actual file extension against a secure allowlist or inspecting the binary signature of the uploaded data, the system accepts the file extension verbatim from the user-supplied input. This lack of sanitization allows an attacker to bypass intended restrictions simply by appending a dangerous executable extension, such as .php, to their upload request.
From an operational perspective, this flaw enables authenticated low-privileged members to achieve remote code execution on the target server. Because the application does not validate whether the uploaded content is actually an image or restricts the destination directory based on file type, it writes the malicious payload directly into the web-accessible uploadfile/ directory. Web servers are typically configured to execute scripts found in these directories when requested via HTTP. Consequently, once a crafted PHP file is successfully stored in this location, an attacker can trigger its execution by sending a specific request to the uploaded script's URL. This transforms what should be a benign image storage feature into a powerful vector for full server compromise, allowing the attacker to run arbitrary commands with the privileges of the web server process.
This vulnerability aligns closely with Common Weakness Enumeration (CWE) categories such as CWE-434, which describes an unrestricted upload of a file with dangerous content, and CWE-79, known as Cross-site Scripting if the uploaded script is used for client-side attacks, though in this context, server-side execution via CWE-94 Improper Control of Generation of Code (Code Injection) is more pertinent. The attack vector also maps to MITRE ATT&CK techniques involving Initial Access through Valid Accounts and Execution via Web Shell deployment. The presence of an authentication requirement does not mitigate the risk significantly because low-privileged accounts are often easier for attackers to obtain or compromise, thereby expanding the potential surface area for exploitation beyond just high-level administrators.
To mitigate this vulnerability, immediate remediation steps must focus on implementing robust file validation mechanisms. Developers should enforce a strict allowlist of permitted image extensions rather than relying on blacklists or verbatim input acceptance. Furthermore, content verification using magic numbers to confirm that the uploaded data matches the expected MIME type for images is essential. The storage location for user uploads should also be reviewed; files should ideally be stored outside the web root or in directories where script execution is explicitly disabled by server configuration directives such as Apache's Options directive or Nginx's try_files rules. Additionally, implementing randomization of uploaded filenames can prevent attackers from predicting file paths and executing them directly, adding a layer of defense-in-depth to complement the primary validation fixes.