CVE-2024-3778

Executive Summary

CVE-2024-3778 is a critical vulnerability in the Ai3 QbiBot application, specifically in its file upload functionality. The software fails to properly restrict the types of files that can be uploaded, allowing an authenticated remote attacker with administrator privileges to upload files containing malicious code. This can lead to remote code execution (RCE), full system compromise, and lateral movement within the network. The CVSS score is 7.2 (High), and no patch or public exploit is currently available. The vulnerability is classified under CWE-434 (Unrestricted Upload of File with Dangerous Type).

CVSS Breakdown & Threat Level

• CVSS Score: 7.2 (High)
• Attack Vector (AV): Network (N)
• Attack Complexity (AC): Low (L)
• Privileges Required (PR): High (H) – requires admin access
• User Interaction (UI): None (N)
• Scope (S): Unchanged (U)
• Confidentiality (C): High (H)
• Integrity (I): High (H)
• Availability (A): High (H)

The threat level is high due to the potential for complete system takeover, but the requirement for administrator privileges reduces the immediate risk to external attackers. However, once an admin account is compromised, the impact is severe.

Deep Dive & Mechanics

The vulnerability resides in the file upload module of Ai3 QbiBot. The application does not validate or restrict the file extension or MIME type of uploaded files. An administrator can upload executable files (e.g., .php, .asp, .jsp, .war) that are then stored on the server and can be executed. This allows the attacker to deploy web shells, backdoors, or other malicious payloads.

The attack flow:

1. Attacker gains admin credentials (via phishing, credential stuffing, or other means).
2. Attacker logs into the QbiBot admin panel.
3. Attacker navigates to the file upload functionality.
4. Attacker uploads a malicious file (e.g., a PHP web shell).
5. The file is stored in a web-accessible directory.
6. Attacker accesses the uploaded file via HTTP, triggering execution of the malicious code.
7. Attacker gains remote code execution on the server.

Vulnerable vs. Patched Code

Since no patch is available, we can only describe the vulnerable behavior:

Vulnerable Code (Conceptual):

// No file type validation
$target_dir = "uploads/";
$target_file = $target_dir . basename($_FILES["file"]["name"]);
move_uploaded_file($_FILES["file"]["tmp_name"], $target_file);

Patched Code (Conceptual):

$allowed_types = array('jpg', 'png', 'gif', 'pdf');
$file_type = strtolower(pathinfo($target_file, PATHINFO_EXTENSION));
if (!in_array($file_type, $allowed_types)) {
    die("File type not allowed.");
}
// Additional checks: MIME type, file content validation, etc.

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

• Target: Ai3 QbiBot instance (vulnerable version)
• Attacker: Kali Linux with common web exploitation tools

Steps:

1. Obtain admin credentials (e.g., via phishing or default credentials).
2. Log in to the QbiBot admin panel.
3. Identify the file upload endpoint (e.g., /admin/upload.php).
4. Create a malicious PHP web shell:

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

5. Upload the file with a .php extension.
6. Access the uploaded file: http://target.com/uploads/shell.php?cmd=id
7. Execute commands and escalate privileges.

No public exploit code is available for this CVE.

Blue Team (Defensive)

Detection:

• Monitor file upload logs for unusual file extensions (e.g., .php, .asp, .jsp).
• Implement file integrity monitoring on upload directories.
• Use WAF rules to block uploads of executable files.

Prevention:

• Restrict file uploads to only allowed types (e.g., images, PDFs).
• Store uploaded files outside the web root.
• Use content-type and magic byte validation.
• Implement strict access controls on admin interfaces.

Indicators of Compromise (IOCs)

• File Hashes (SHA256): (None available; generate upon discovery)
• Network Indicators:
  • POST requests to /admin/upload.php with multipart/form-data containing .php or .asp files.
  • Subsequent GET requests to /uploads/*.php?cmd=...
• File System Indicators:
  • Unexpected files in the uploads directory with executable extensions.
  • Web shells or backdoors in web-accessible directories.
• Log Indicators:
  • Admin login from unusual IP addresses.
  • File upload events with suspicious file names or extensions.

Detection Engineering

YARA Rule

rule CVE_2024_3778_WebShell_Upload {
    meta:
        description = "Detects web shell upload attempts targeting CVE-2024-3778"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-3778"
    strings:
        $php_shell = "<?php" nocase
        $asp_shell = "<%" nocase
        $jsp_shell = "<%" nocase
        $cmd_param = "cmd=" nocase
        $exec_func = /system|exec|shell_exec|passthru|popen/ nocase
    condition:
        any of ($php_shell, $asp_shell, $jsp_shell) and
        any of ($cmd_param, $exec_func)
}

Sigma Rule

title: Suspicious File Upload to QbiBot Admin
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects upload of executable files to Ai3 QbiBot admin panel
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        http_method: POST
        url_path: '/admin/upload.php'
        file_extension:
            - '.php'
            - '.asp'
            - '.jsp'
            - '.war'
            - '.exe'
    condition: selection
falsepositives:
    - Legitimate admin uploading necessary scripts (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2024-3778 - Suspicious file upload to QbiBot admin";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/admin/upload.php"; http_uri;
    content:".php"; http_client_body;
    classtype:web-application-attack;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Disable file upload functionality in QbiBot if not required.
2. Restrict admin access to trusted IP addresses only.
3. Implement strong authentication (MFA) for admin accounts.

Long-term Fixes:

• Apply vendor patch when available.
• Implement file type whitelisting and content validation.
• Store uploaded files in a non-web-accessible directory and serve them via a script that enforces MIME types.
• Regularly audit admin accounts and file upload logs.

Workarounds:

• Use a Web Application Firewall (WAF) to block uploads of executable files.
• Deploy endpoint detection and response (EDR) to monitor for web shell activity.

Valters IT