[Solved] Fiddler Classic and everywhere blocked by CloudFront

[Kyle Watson]

Tried multiple browsers but always receive from booking.com when inspecting traffic:

 

HTTP/1.1 403 Forbidden
Server: CloudFront
Date: Mon, 19 Oct 2026 19:55:37 GMT
Content-Type: text/html
Content-Length: 919
Connection: keep-alive
X-Cache: Error from cloudfront
Via: 1.1 fc20c1482245d494719df97cc96116e0.cloudfront.net (CloudFront)
X-Amz-Cf-Pop: PHX52-P3
X-Amz-Cf-Id: _nmq3w2vKtiW70wXoSzzLJMBavMsrHTE7odnkCrEVoQgzrdV_iQ7iA==
Strict-Transport-Security: max-age=63072000; includeSubDomains; preload
Accept-CH: ECT

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<HTML><HEAD><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
<TITLE>ERROR: The request could not be satisfied</TITLE>
</HEAD><BODY>
<H1>403 ERROR</H1>
<H2>The request could not be satisfied.</H2>
<HR noshade size="1px">
Request blocked.
We can't connect to the server for this app or website at this time. There might be too much traffic or a configuration error. Try again later, or contact the app or website owner.
<BR clear="all">
If you provide content to customers through CloudFront, you can find steps to troubleshoot and help prevent this error by reviewing the CloudFront documentation.
<BR clear="all">
<HR noshade size="1px">
<PRE>
Generated by cloudfront (CloudFront)
Request ID: _nmq3w2vKtiW70wXoSzzLJMBavMsrHTE7odnkCrEVoQgzrdV_iQ7iA==
</PRE>
<ADDRESS>
</ADDRESS>
</BODY></HTML>

 

Any work around?

[Nick Iliev]

Hello Kyle,

 

Thank you for the details and the full response headers.

What the response shows

The 403 is generated by Amazon CloudFront ( Server: CloudFront ,  X-Cache: Error from cloudfront , "Generated by cloudfront"). It is not a Fiddler error. The request was rejected at booking.com's CDN edge, before it reached their application servers. Booking.com uses bot and WAF protection, and this generic "Request blocked" page is typical of a security rule.

Our testing

We opened booking.com on our side with Fiddler Classic and could not reproduce the block. The block depends on something specific to your network environment.

Likely causes

1. Network and IP. CloudFront decides largely on IP reputation and region. VPN, datacenter or corporate IPs are blocked more often. So are IPs that sent many requests during repeated testing. Such blocks can last several hours.
2. Chained proxy, VPN or security software. An upstream proxy, antivirus or corporate gateway changes the IP and TLS fingerprint that booking.com sees.
3. Modified requests. Rules, AutoResponder entries or changed headers can make requests look suspicious.

What you can try

1. Open booking.com in the browser with Fiddler closed. If it also fails, the cause is your network or IP, not Fiddler.
2. Try another network, such as a mobile hotspot, and turn off any VPN. If the IP was rate limited, wait a few hours.
3. Check for a chained proxy: in Fiddler go to Tools > Options > Gateway and check the system proxy settings. Remove any upstream proxy if possible.
4. Disable rules, AutoResponder entries and filters.
5. In Tools > Options > HTTPS, try a different TLS protocol selection.
6. Temporarily disable antivirus or HTTPS scanning, if your policy allows it.
7. As a workaround, add  *.booking.com  to the "Skip decryption for the following hosts" list in Tools > Options > HTTPS. The site should load, but you won't see decrypted traffic for it.
8. If the block persists, contact booking.com support and give them the CloudFront Request ID  _nmq3w2vKtiW70wXoSzzLJMBavMsrHTE7odnkCrEVoQgzrdV_iQ7iA==  so they can check the rule or allowlist your IP.

 

Regards,
Nick Iliev
Progress Telerik

[Kyle Watson]

1. Works without fiddler

2. I tried another network still same

3. Uses default system proxy

4. All empty

5. Tried different tls

6. Don't know what this is, don't think it's that.

7. Defeats the entire purpose

8. Getting support from booking.com is a joke, sadly.

 

 

Thanks for trying Nick. I can use chrome's network viewer that does work but it's just not as good.

 

[Nick Iliev]

Hey Kyle,

 

You can try to explicitly enable the HTTP/2 support and the "Enable Authentication" options in Fiddler Everywhere (HTTP/2 is not supported in Fiddler Classic). This will effectively change the fingerpringting and will also establish a connection to booking.com through different protocols

[Kyle Watson]

I tried that in fiddler everywhere but still no luck, still getting 403 forbidden.

I was able to do the work through chromes dev tooling which all works it's just not nearly as good as fiddler. Not sure what my environment is doing that differs from yours that it's not working but....oh well. 

Thank you for your suggestions.