Lab: Web cache poisoning with multiple headers
This lab contains a web cache poisoning vulnerability that is only exploitable when you use multiple headers to craft a malicious request. A user visits the home page roughly once a minute. To solve this lab, poison the cache with a response that executes
alert(document.cookie) in the visitor's browser.
Tip: This lab supports both the
- With Burp running, load the website's home page.
Go to "Proxy" > "HTTP history" and study the requests and responses that you generated. Find the
/resources/js/tracking.jsand send it to Burp Repeater.
Add a cache-buster query parameter and the
X-Forwarded-Hostheader with an arbitrary hostname, such as
example.com. Notice that this doesn't seem to have any effect on the response.
X-Forwarded-Hostheader and add the
X-Forwarded-Schemeheader instead. Notice that if you include any value other than
HTTPS, you receive a 302 response. The
Locationheader shows that you are being redirected to the same URL that you requested, but using
X-Forwarded-Host: example.comheader back to the request, but keep
X-Forwarded-Scheme: nothttpsas well. Send this request and notice that the
Locationheader of the 302 redirect now points to
Go to the exploit server and change the file name to match the path used by the vulnerable response:
In the body, enter the payload
alert(document.cookie)and store the exploit.
Go back to the request in Burp Repeater and set the
X-Forwarded-Hostheader as follows, remembering to enter your own exploit server ID:
Make sure the
X-Forwarded-Schemeheader is set to anything other than
Send the request until you see your exploit server URL reflected in the response and
X-Cache: hitin the headers.
To check that the response was cached correctly, right-click on the request in Burp, select "Copy URL", and load this URL in your browser. If the cache was successfully poisoned, you will see the script containing your payload,
alert(document.cookie). Note that the
alert()won't actually execute here.
- Go back to Burp Repeater, remove the cache buster, and resend the request until you poison the cache again.
To simulate the victim, reload the home page in your browser and make sure that the
- Keep replaying the request to keep the cache poisoned until the victim visits the site and the lab is solved.