CVE-2024-6866
📋 TL;DR
This vulnerability in flask-cors 4.01 allows unauthorized origins to bypass CORS restrictions due to case-insensitive path matching. Attackers can access restricted API endpoints, potentially exposing sensitive data. Any application using the vulnerable version with CORS path restrictions is affected.
💻 Affected Systems
- corydolphin/flask-cors
📦 What is this software?
Flask Cors by Flask Cors Project
⚠️ Risk & Real-World Impact
Worst Case
Complete data exposure from restricted API endpoints, enabling attackers to steal sensitive information or perform unauthorized actions.
Likely Case
Partial data leakage from misconfigured endpoints, potentially exposing user data or internal information.
If Mitigated
Limited impact with proper authentication and additional security layers, though CORS bypass remains possible.
🎯 Exploit Status
Exploitation requires knowledge of restricted paths and ability to craft requests from unauthorized origins.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 4.0.2 or later
Vendor Advisory: https://github.com/corydolphin/flask-cors/security/advisories/GHSA-4w8f-7prg-5vq9
Restart Required: No
Instructions:
1. Update flask-cors: pip install --upgrade flask-cors>=4.0.2
2. Verify the version: pip show flask-cors
3. No application restart required for Python applications using dynamic imports.
🔧 Temporary Workarounds
Implement custom CORS path validation
allAdd middleware to validate path case-sensitivity before CORS processing
# Add custom request handler to validate paths
from flask import request
@app.before_request
def validate_path_case():
if request.path.lower() != request.path:
return 'Invalid path', 400
🧯 If You Can't Patch
- Disable CORS path restrictions and rely on authentication/authorization
- Implement reverse proxy with proper path validation before reaching application
🔍 How to Verify
Check if Vulnerable:
Check installed version: pip show flask-cors | grep VersionCheck Version:
pip show flask-cors | grep VersionVerify Fix Applied:
Confirm version is 4.0.2 or higher and test CORS path restrictions with case variations📡 Detection & Monitoring
Log Indicators:
- Multiple 200/204 responses to similar paths with different cases from unauthorized origins
- CORS preflight requests with case-varied paths
Network Indicators:
- Cross-origin requests to restricted paths with case variations
- Increased CORS preflight traffic
SIEM Query:
source="web_logs" AND (path:*[A-Z]* OR origin!="allowed_origin") AND response_code=200