Issue
Websites behind Cloudflare proxied mode may intermittently return Cloudflare 521 Web Server Is Down errors when Imunify360 WebShield is enabled.
In some cases, Cloudflare 520 or 522 errors may also be reported.
The issue may appear randomly during regular browsing, website editing, or repeated page refreshes. Customers may report that the website becomes accessible again after WebShield or Imunify360 services are disabled.
Environment
- Imunify360
- WebShield
- CloudLinux
- Cloudflare proxied traffic
Solution
The issue is currently under investigation by the Imunify360 development team.
A WebShield release that may contain the fix is being verified. Check whether the server has imunify360-webshield-bundle-1.41.2 or later installed. If the package is already updated, re-enable WebShield and test again.
rpm -q imunify360-webshield-bundle.As a temporary mitigation, WebShield can be disabled if the customer confirms that Cloudflare errors stop when WebShield is disabled. This should be used only as a temporary workaround until the fix is confirmed.
Cause
The current investigation is related to WebShield handling of Cloudflare-proxied traffic and CAPTCHA/IP list behavior. In the reported cases, Cloudflare errors appeared when Imunify360 WebShield was enabled and stopped or decreased when WebShield or Imunify360 services were disabled.
Useful links
- Related internal task:
DEF-44257 - Release/task reference:
RE-3772
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