CVE-2022-31514: Fan Platform Path Traversal Vulnerability

CVE-2022-31514 Overview

CVE-2022-31514 is a critical path traversal vulnerability affecting the Caoyongqi912/Fan_Platform repository. The vulnerability exists due to unsafe usage of the Flask send_file function, which allows attackers to perform absolute path traversal attacks. This flaw enables remote, unauthenticated attackers to read arbitrary files from the server's file system by manipulating file path parameters.

Critical Impact

Remote attackers can exploit this vulnerability to read sensitive files from the server without authentication, potentially exposing configuration files, credentials, source code, and other confidential data.

Affected Products

• Fan_platform_project Fan Platform (through 2021-04-20)

Discovery Timeline

• 2022-07-11 - CVE CVE-2022-31514 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-31514

Vulnerability Analysis

This path traversal vulnerability (CWE-22) stems from improper handling of user-supplied file paths in the Flask web application. The send_file function, when used without proper input validation, allows attackers to break out of the intended directory structure and access files anywhere on the file system that the web server process has permission to read.

The vulnerability is particularly dangerous because it can be exploited remotely over the network without requiring any authentication or user interaction. An attacker with network access to the vulnerable application can craft malicious requests containing directory traversal sequences to navigate outside the web root and retrieve sensitive system files.

Root Cause

The root cause of this vulnerability is the unsafe use of Flask's send_file function without proper validation or sanitization of user-controlled input. When file path parameters are passed directly to send_file without checking for traversal sequences (such as ../ or absolute paths), the application will serve any file the server process can access. Flask's send_file function does not inherently restrict file access to a specific directory, making proper input validation critical for secure implementation.

Attack Vector

The attack vector is network-based, requiring no authentication or privileges. An attacker can exploit this vulnerability by sending HTTP requests with manipulated file path parameters containing absolute paths or directory traversal sequences. For example, an attacker might craft a request that includes /../../../etc/passwd to escape the intended directory and access the system's password file.

The vulnerability allows attackers to:

• Read sensitive configuration files containing database credentials or API keys
• Access application source code to discover additional vulnerabilities
• Retrieve system files to enumerate the server environment
• Potentially access private keys or certificates stored on the file system

For technical details on this vulnerability class, see the GitHub Security Lab discussion.

Detection Methods for CVE-2022-31514

Indicators of Compromise

• HTTP request logs containing path traversal sequences such as ../, ..%2f, or %2e%2e/ in file-related parameters
• Requests attempting to access sensitive system files like /etc/passwd, /etc/shadow, or Windows system files
• Unusual access patterns to the Flask application's file download endpoints
• Server responses returning content from outside the expected web directory

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block path traversal patterns in request parameters
• Deploy intrusion detection systems (IDS) with signatures for directory traversal attacks
• Monitor application logs for requests containing encoded or decoded traversal sequences
• Use runtime application self-protection (RASP) solutions to detect file access outside expected directories

Monitoring Recommendations

• Enable verbose logging for all file access operations in the Flask application
• Set up alerts for access attempts to sensitive file paths from web application processes
• Monitor for anomalous file read operations by the web server user account
• Implement file integrity monitoring on critical system and configuration files

How to Mitigate CVE-2022-31514

Immediate Actions Required

• Update the Fan_Platform application to a version that properly validates file paths if a patched version is available
• Implement network-level access controls to restrict access to the vulnerable application
• Deploy a web application firewall with rules to block path traversal attempts
• Review and restrict file system permissions for the web server process

Patch Information

As of the last available information, no official patch has been released for this vulnerability. The affected repository (Caoyongqi912/Fan_Platform through 2021-04-20 on GitHub) should be reviewed for any updates. Organizations using this software should consider implementing manual code fixes or migrating to alternative solutions.

For additional context, refer to the GitHub Security Lab discussion.

Workarounds

• Use Flask's safe_join function from werkzeug.utils to safely construct file paths before passing to send_file
• Implement strict input validation to reject any paths containing traversal sequences or absolute paths
• Configure the application to serve files only from a designated directory using send_from_directory instead of send_file
• Apply the principle of least privilege to the web server process to minimize the impact of successful exploitation

# Secure file serving example using Flask
from flask import Flask, abort
from werkzeug.utils import safe_join, send_from_directory
import os

app = Flask(__name__)
UPLOAD_FOLDER = '/var/www/app/uploads'

@app.route('/download/<filename>')
def secure_download(filename):
    # Use safe_join to prevent path traversal
    safe_path = safe_join(UPLOAD_FOLDER, filename)
    if safe_path is None or not os.path.isfile(safe_path):
        abort(404)
    return send_from_directory(UPLOAD_FOLDER, filename)