{"id":36644,"date":"2024-09-30T07:10:37","date_gmt":"2024-09-30T07:10:37","guid":{"rendered":"https:\/\/www.wpstaq.com?post_type=knowledgebase&p=36644"},"modified":"2024-12-10T05:58:39","modified_gmt":"2024-12-10T05:58:39","slug":"cloudflare-520-error","status":"publish","type":"knowledgebase","link":"https:\/\/www.wpstaq.com\/sg\/knowledgebase\/cloudflare-520-error\/","title":{"rendered":"Cloudflare 520 or 521 error"},"content":{"rendered":"

Cloudflare errors 520<\/strong> and 521<\/strong> can occur when there is an issue with the connection between Cloudflare and the origin server. These errors are often related to the Staq Firewall blocking malicious traffic or other unexpected responses from the server. Below is an explanation of each error and steps to resolve them.<\/p>\n

Cloudflare 520 Error<\/h2>\n

Cloudflare defines a 520 error<\/strong> as: “Error 520 occurs when the origin server returns an empty, unknown, or unexpected response to Cloudflare.”<\/p>\n

Understanding the Cause<\/h3>\n

This error typically occurs when the Staq server returns a 503 error<\/strong>. Since all traffic is routed through Cloudflare, users see a 520 error<\/strong> instead.<\/p>\n

Steps to Resolve<\/h3>\n
    \n
  1. Determine Why the User Was Blocked<\/strong>:A 503 error<\/strong> on Staq\u2019s end indicates that the user was blocked by the Staq Firewall. To identify the reason for the block, refer to this guide:
    \nWhy Was an IP Address Blocked by Staq Firewall?<\/a><\/li>\n
  2. Unban the IP Address (If Necessary)<\/strong>:If the block was a mistake, follow this guide to unban the IP:
    \n    Unban an IP in Firewall from the Staq Interface<\/a>.<\/li>\n<\/ol>\n

    Cloudflare 521 Error<\/h2>\n

    Cloudflare defines a 521 error<\/strong> as: “Error 521 occurs when the origin server refuses the connection from Cloudflare.”<\/p>\n

    Understanding the Cause<\/h3>\n

    This error occurs when blacklisted IPs (often malicious bots or users) are flagged and blocked by the Staq Firewall. Cloudflare, acting as a proxy, forwards the real user\u2019s IP via headers like X-Forwarded-For<\/strong> or X-Real-IP<\/strong>. If the forwarded IP is blacklisted, the connection is denied, resulting in a 521 error<\/strong>.<\/p>\n

    Important Note:<\/strong> Cloudflare\u2019s official IP ranges are whitelisted by default in Staq\u2019s firewall, ensuring that Cloudflare itself is never blocked:<\/p>\n