MihChe

Hey Patrick,

Thanks for your update. As I expected, yes, this can happen on NGINX servers and I was able to replicate this on one of my servers.

When the form get submitted, the reCaptcha token is submitted to the server as well. Which makes sense, because it should be verified on the server side. Sometimes, especially when Google shows the challenge, the encrypted token is extremely long and when NGINX receives such request it will reject it. This causes 502 Bad Gateway error.

All you have to do is to increase the values of client_body_buffer_size and client_max_body_size directives in nginx.conf.

This is what works for me, but as I mentioned, the values can differ from site to site
client_body_buffer_size 16K;
client_max_body_size 16K;

If FastCGI is enabled you can also increase the values of fastcgi_buffers and fastcgi_buffer_size directives

My values are:

fastcgi_buffers 8 16k;
fastcgi_buffer_size 32k;

Please let me know!

Cheers,
~Mihai

What do you mean by starting the session?

So… Google shows the captcha challenge and when you click “Verify” you are getting the 502 Bad Gateway error, right?

Are you using NGINX?

~Mihai

Hi @gustavowiesner,
Is this happening when you post the form? If this is the case, the 502 Bad Gateway error tells me something else. Are you using NGINX somehow – as web server or proxy?

~Mihai