CVE-2024-1527: CMS Made Simple RCE Vulnerability

CVE-2024-1527 Overview

CVE-2024-1527 is an unrestricted file upload vulnerability in CMS Made Simple version 2.2.14. The flaw exists in the upload functionality and allows an authenticated user to bypass file type restrictions. An attacker can leverage this weakness to upload a webshell and achieve remote command execution on the underlying server. The issue is tracked under CWE-434: Unrestricted Upload of File with Dangerous Type. Details were published in an INCIBE Security Notice covering multiple flaws in the product.

Critical Impact
Authenticated attackers can upload arbitrary files and execute operating system commands through a webshell, resulting in full compromise of the hosting environment.

Affected Products

CMS Made Simple 2.2.14
Deployments using the affected upload functionality
Web servers hosting the vulnerable CMS installation

Discovery Timeline

2024-03-12 - CVE-2024-1527 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2024-1527

Vulnerability Analysis

The vulnerability resides in the file upload handler of CMS Made Simple 2.2.14. Server-side validation does not correctly restrict dangerous file types accepted by the upload endpoint. An authenticated user with access to the upload functionality can submit a file whose extension or MIME type would normally be rejected. Once written to a web-accessible directory, the file can be requested through the browser and interpreted by the PHP runtime. This turns a content management action into arbitrary command execution on the host.

Exploitation requires only low-privilege authenticated access over the network. No user interaction is needed beyond the attacker's own session. Successful exploitation compromises the confidentiality, integrity, and availability of the site and any data it can reach.

Root Cause

The root cause is missing or insufficient validation of uploaded file content, extension, and MIME type in the upload workflow. The application relies on client-controlled attributes and does not enforce a strict allow-list of safe extensions. Files placed on disk retain executable extensions such as .php, allowing the web server to hand them to the PHP interpreter.

Attack Vector

The attack proceeds over HTTP or HTTPS against an authenticated CMS Made Simple session. The attacker uploads a PHP webshell disguised as an allowed asset, then issues an HTTP request to the uploaded file's URL. The web server executes the shell, giving the attacker command execution under the web server user. From that foothold, attackers can pivot to database credentials, config files, and other tenants on the host. Refer to the INCIBE Security Notice for further technical context.

Detection Methods for CVE-2024-1527

Indicators of Compromise

New or unexpected files with executable extensions such as .php, .phtml, or .phar inside CMS Made Simple upload directories.
HTTP POST requests to the admin upload endpoint followed by GET requests to newly created files under /uploads/ or /tmp/.
Outbound network connections from the web server process to unfamiliar hosts shortly after an upload event.

Detection Strategies

Monitor web server access logs for requests to files inside upload directories whose extensions imply server-side execution.
Alert on process creation events where the web server user spawns shells (sh, bash, cmd.exe) or reconnaissance binaries.
Use file integrity monitoring on CMS Made Simple asset directories to detect the appearance of scripts outside of a normal deployment window.

Monitoring Recommendations

Enable verbose logging on the CMS Made Simple admin module to record upload actions, submitting user, and stored filename.
Forward web server and host telemetry to a central analytics platform for correlation between authentication, upload, and execution events.
Review authenticated admin sessions regularly and investigate accounts that perform bulk uploads or access uploads from unusual geographies.

How to Mitigate CVE-2024-1527

Immediate Actions Required

Restrict access to the CMS Made Simple admin console to trusted networks or VPN users until a patched release is deployed.
Audit all accounts with upload privileges and revoke access that is not strictly required.
Inspect upload directories for unauthorized scripts and remove any suspicious files after preserving forensic copies.

Patch Information

No fixed version is listed in the referenced advisory data for CVE-2024-1527. Monitor the CMS Made Simple project and the INCIBE Security Notice for updates, and upgrade beyond version 2.2.14 as soon as a corrected release is available.

Workarounds

Configure the web server to deny execution of scripts within upload directories using rules such as Apache php_flag engine off or an Nginx location block that returns static content only.
Enforce a strict allow-list of file extensions at a reverse proxy or web application firewall in front of the CMS.
Rotate administrative credentials and require multi-factor authentication on the identity provider used for CMS Made Simple admin access.

bash

# Example Nginx configuration to prevent script execution in upload paths
location ^~ /uploads/ {
    default_type text/plain;
    location ~ \.(php|phtml|phar|pl|py|jsp|cgi)$ {
        deny all;
        return 403;
    }
}