CVE-2025-2653

Executive Summary

CVE-2025-2653 is a problematic vulnerability identified in FoxCMS version 1.25. The flaw resides in an unknown functionality that leads to improper authorization (CWE-285). An attacker can exploit this remotely, and a public proof-of-concept (PoC) has been released, increasing the risk of active exploitation. The vendor has not yet released a patch, leaving all instances of FoxCMS 1.25 vulnerable.

Supply Chain & Package Security

FoxCMS is a PHP-based content management system. While not distributed via NPM, PyPI, Go, or Ruby registries, its dependencies (e.g., PHP libraries, Composer packages) may introduce additional risks. Organizations using FoxCMS should audit their entire PHP dependency tree for known vulnerabilities and ensure all third-party libraries are up to date.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (No official vector assigned)
• Threat Level: Medium (based on public PoC and remote attack vector)
• 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: None (A:N)

Deep Dive & Mechanics

The vulnerability stems from improper authorization checks in an unknown component of FoxCMS 1.25. The exact endpoint or function is not disclosed, but the manipulation allows an attacker to bypass access controls and perform unauthorized actions. Since the attack is remote and requires no authentication, it can be exploited by any unauthenticated user.

The public PoC likely demonstrates how to craft a malicious request (e.g., HTTP GET/POST) to a specific URL that triggers the authorization bypass. This could allow an attacker to:

• Access administrative functions without login.
• Modify or delete content.
• Retrieve sensitive configuration data.

Vulnerable vs. Patched Code

Since no patch is available, a direct code comparison is not possible. However, the vulnerable code likely lacks proper session validation or role-based access checks. A patched version would implement:

// Vulnerable code (conceptual)
if ($_GET['action'] == 'admin') {
    // No authentication check
    performAdminAction();
}

// Patched code (conceptual)
session_start();
if ($_SESSION['role'] == 'admin') {
    if ($_GET['action'] == 'admin') {
        performAdminAction();
    }
} else {
    header('HTTP/1.0 403 Forbidden');
    exit;
}

Exploitation & Lab Setup

Red Team

1. Setup: Deploy FoxCMS 1.25 in a controlled environment (e.g., Docker container).
2. Reconnaissance: Use Shodan dorks to find live instances.
3. Exploitation: Send a crafted HTTP request to the vulnerable endpoint. Example using curl:

curl -X GET "http://target.com/index.php?action=admin&cmd=delete&id=1"

If the request succeeds without authentication, the vulnerability is confirmed.

4. Post-Exploitation: Attempt to escalate privileges or extract sensitive data (e.g., database credentials from config files).

Blue Team

1. Detection: Monitor for unusual HTTP requests to administrative endpoints without prior login.
2. Honeypot: Deploy a fake FoxCMS instance to capture attacker behavior.
3. Mitigation: Implement a Web Application Firewall (WAF) rule to block requests to unknown or suspicious endpoints.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests to /index.php?action=admin or similar patterns.
  • Unusual POST data containing cmd=delete or cmd=update.
• File IOCs:
  • Modified config.php or users.php files.
  • New admin users in the database.
• Log IOCs:
  • Access logs showing 200 responses to unauthorized admin actions.
  • Error logs with 403 Forbidden followed by successful admin actions.

Detection Engineering

YARA Rule

rule FoxCMS_Authorization_Bypass {
    meta:
        description = "Detects FoxCMS 1.25 authorization bypass attempts"
        author = "Valters IT"
        date = "2025-03-15"
        reference = "CVE-2025-2653"
    strings:
        $s1 = "action=admin" nocase
        $s2 = "cmd=delete" nocase
        $s3 = "cmd=update" nocase
    condition:
        any of ($s*) and filesize < 10KB
}

Sigma Rule

title: FoxCMS Authorization Bypass Attempt
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects HTTP requests targeting FoxCMS admin functions without authentication
author: Valters IT
date: 2025/03/15
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-2653
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains: 'action=admin'
    condition: selection
falsepositives:
    - Legitimate admin access after authentication
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"FoxCMS Authorization Bypass Attempt"; flow:to_server,established; content:"GET"; http_method; content:"action=admin"; http_uri; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate: Disable or restrict access to FoxCMS admin panels via firewall rules (e.g., allow only from trusted IPs).
2. Short-term: Apply a virtual patch using a WAF to block requests containing action=admin or similar patterns.
3. Long-term: Monitor the vendor for an official patch. If none is released, consider migrating to an alternative CMS.
4. Compensating Controls: Implement strong authentication (e.g., multi-factor) and strict session management.

Valters IT
Securing Digital Frontiers