(Plesk) Mod_security

Hi guys,

For weeks I’m hit with 520/521 CF errrors on my domain. I tried all of the supplied solutions (whitelisting etc) .

Since I have mod_security enabled via Plesk interface could this interfere with Cloudflare thus making the webserver at time unreachable? Besided this issue should it been enabled when using CF which also comes with it it’s own FW.

Hi there,

520 would be due to your webserver sending something abnormal. a 521 would be webserver appearing as down when we try to connect.

These could both be connected to the mod_security you’re describing within Plesk or it could be unrelated, trial and error would be best to test theories. EG: does your site work perfectly with mod_security off, if yes, then it probably is mod_security.

I’ve used Plesk extensively myself in the past.

My advice here would be to check the mod_security logging to see if you can see the reasoning behind it.

That should help you in terms of fixing the issue at your origin webserver.

If you are on a Cloudflare paid plan then our WAF would be great in terms of protection.

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