Elasticsearch CORS policy errors in Kibana - Common Causes & Fixes

Brief Explanation

CORS (Cross-Origin Resource Sharing) policy errors occur when Kibana, running on one domain, attempts to make requests to Elasticsearch running on a different domain or port. These errors are security measures implemented by web browsers to prevent potentially malicious cross-origin requests.

Impact

CORS policy errors can significantly impact the functionality of Kibana:

• Prevent Kibana from communicating with Elasticsearch
• Disrupt data visualization and analysis capabilities
• Hinder user ability to manage indices, perform searches, or configure Elasticsearch through Kibana

Common Causes

1. Misconfigured CORS settings in Elasticsearch
2. Incorrect URL or port settings in Kibana configuration
3. Use of different protocols (http vs https) for Kibana and Elasticsearch
4. Firewall or proxy interference
5. Elasticsearch running on a different domain than Kibana

Troubleshooting and Resolution Steps

1. Verify Elasticsearch CORS settings:

   • Check elasticsearch.yml for proper CORS configuration
   • Ensure http.cors.enabled is set to true
   • Configure http.cors.allow-origin to include Kibana's URL

2. Review Kibana configuration:

   • Confirm elasticsearch.hosts in kibana.yml points to the correct Elasticsearch URL
   • Ensure protocol (http/https) matches between Kibana and Elasticsearch

3. Check network settings:

   • Verify no firewall rules are blocking communication
   • Ensure proper proxy configuration if applicable

4. Use matching protocols:

   • Configure both Kibana and Elasticsearch to use either http or https

5. Restart services:

   • After making configuration changes, restart both Elasticsearch and Kibana

6. Check browser console:

   • Examine the browser's developer tools for specific CORS error messages

Best Practices

• Always use HTTPS in production environments
• Regularly review and update CORS settings as your infrastructure changes
• Implement proper authentication mechanisms alongside CORS settings
• Keep Elasticsearch and Kibana versions in sync to avoid compatibility issues

Frequently Asked Questions

Q: How do I enable CORS in Elasticsearch?
A: Add the following to your elasticsearch.yml file:

http.cors.enabled: true
http.cors.allow-origin: "http://kibana-domain.com:5601"
http.cors.allow-methods: OPTIONS, HEAD, GET, POST, PUT, DELETE
http.cors.allow-headers: X-Requested-With, X-Auth-Token, Content-Type, Content-Length

Q: Can CORS errors occur even if Kibana and Elasticsearch are on the same server?
A: Yes, if they're accessed through different ports or protocols (http vs https), CORS errors can still occur.

Q: How do I troubleshoot CORS errors in Kibana?
A: Check the browser's developer console for specific error messages, verify Elasticsearch CORS settings, and ensure Kibana's configuration correctly points to Elasticsearch.

Q: Are CORS settings in Elasticsearch a security risk?
A: While CORS settings can introduce security risks if misconfigured, they're necessary for Kibana to function properly. Always use specific origins rather than wildcard (*) in production environments.

Q: How can I test if my CORS settings are working correctly?
A: You can use tools like cURL or Postman to send requests with custom origins to your Elasticsearch instance and verify the responses include the correct CORS headers.