CVE-2022-31588: Testplatform Path Traversal Vulnerability

CVE-2022-31588 Overview

CVE-2022-31588 is an absolute path traversal vulnerability affecting the zippies/testplatform repository on GitHub. The vulnerability exists due to unsafe usage of Flask's send_file function, which allows attackers to read arbitrary files from the server's filesystem by manipulating file path parameters.

Critical Impact

This path traversal vulnerability enables unauthenticated remote attackers to access sensitive files outside the intended directory, potentially exposing configuration files, credentials, source code, and other confidential data stored on the affected server.

Affected Products

• testplatform_project testplatform (versions through 2016-07-19)

Discovery Timeline

• 2022-07-11 - CVE-2022-31588 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-31588

Vulnerability Analysis

This vulnerability is classified as CWE-22 (Improper Limitation of a Pathname to a Restricted Directory), commonly known as path traversal or directory traversal. The root issue lies in how the testplatform application handles user-supplied file paths when serving files through Flask's send_file function.

When Flask's send_file function is invoked without proper validation of the file path argument, attackers can craft malicious requests containing directory traversal sequences or absolute paths to access files outside the application's intended web root. This can lead to unauthorized disclosure of sensitive system files, application configuration data, database credentials, and other confidential information stored on the server.

The network-based attack vector with no authentication requirements makes this vulnerability particularly dangerous, as any remote attacker with network access to the application can exploit it without needing valid credentials or user interaction.

Root Cause

The vulnerability stems from insufficient input validation when processing file path parameters passed to Flask's send_file function. The application fails to properly sanitize or restrict user-controlled input, allowing attackers to escape the intended directory structure using absolute paths (e.g., /etc/passwd) or relative path traversal sequences (e.g., ../../../etc/passwd).

Flask's send_file function, when used without setting the safe_join parameter or implementing path validation, will serve any file accessible to the application's process, regardless of whether it resides within the intended web directory.

Attack Vector

The attack is conducted over the network against the vulnerable Flask application. An attacker can exploit this vulnerability by:

1. Identifying endpoints that serve files using the vulnerable send_file implementation
2. Crafting HTTP requests with malicious file path parameters containing absolute paths or traversal sequences
3. Accessing sensitive files such as /etc/passwd, application configuration files, or database credentials

Since this is a path traversal vulnerability with no code examples available, the exploitation involves sending HTTP requests with manipulated file path parameters. For detailed technical information, refer to the GitHub Security Lab Discussion.

Detection Methods for CVE-2022-31588

Indicators of Compromise

• HTTP requests containing path traversal sequences such as ../, ..%2f, ..%252f, or URL-encoded variations targeting file-serving endpoints
• Access logs showing requests for system files like /etc/passwd, /etc/shadow, or Windows equivalents
• Unusual file access patterns in application logs indicating attempts to read files outside the web root
• Error messages or stack traces revealing full filesystem paths in server responses

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block path traversal patterns in URL parameters
• Configure intrusion detection systems (IDS) to alert on requests containing directory traversal sequences
• Enable verbose logging on file-serving endpoints and monitor for suspicious file path requests
• Conduct regular code reviews to identify unsafe usage of Flask's send_file function

Monitoring Recommendations

• Monitor HTTP access logs for patterns indicative of directory traversal attempts
• Set up alerts for any successful access to sensitive system files through the application
• Track unusual spikes in 403/404 responses that may indicate reconnaissance activity
• Implement file integrity monitoring on sensitive configuration files

How to Mitigate CVE-2022-31588

Immediate Actions Required

• Identify all endpoints using Flask's send_file function and review their input validation
• Implement strict input validation and path sanitization for all user-supplied file path parameters
• Use Flask's safe_join function to securely construct file paths within a designated directory
• Consider restricting file access to a specific whitelist of allowed files

Patch Information

The zippies/testplatform repository on GitHub appears to be unmaintained (last updated 2016-07-19). No official vendor patch is available for this vulnerability. Organizations using this code should implement their own mitigations or migrate to actively maintained alternatives.

For additional context on this vulnerability class, refer to the GitHub Security Lab Discussion.

Workarounds

• Replace unsafe send_file usage with send_from_directory which restricts file serving to a specific directory
• Implement a whitelist approach, only allowing access to explicitly defined files
• Add input validation to reject paths containing traversal sequences or absolute paths
• Deploy a web application firewall (WAF) to block path traversal attack patterns

# Example secure Flask configuration using send_from_directory
# Instead of: send_file(user_supplied_path)
# Use: send_from_directory(app.config['UPLOAD_FOLDER'], filename)

# Ensure UPLOAD_FOLDER is set to a restricted directory
export FLASK_UPLOAD_FOLDER=/var/www/app/uploads

# Additional validation can be added:
# - Validate filename against allowed patterns
# - Use werkzeug.utils.secure_filename() to sanitize filenames
# - Implement access controls to verify user authorization