Web Cache Poisoning Affecting rack package, versions <3.0.0.beta1


Severity

Recommended
0.0
medium
0
10

CVSS assessment made by Snyk's Security Team. Learn more

Threat Intelligence

Exploit Maturity
Proof of concept

Do your applications use this vulnerable package?

In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.

Test your applications
  • Snyk IDSNYK-RUBY-RACK-1061917
  • published19 Apr 2021
  • disclosed13 Oct 2020
  • creditJames Kettle

Introduced: 13 Oct 2020

CVE NOT AVAILABLE CWE-444  (opens in a new tab)
First added by Snyk

How to fix?

Upgrade rack to version 3.0.0.beta1 or higher.

Overview

rack is a minimal, modular and adaptable interface for developing web applications in Ruby. By wrapping HTTP requests and responses in the simplest way possible, it unifies and distills the API for web servers, web frameworks, and software in between (the so-called middleware) into a single method call.

Affected versions of this package are vulnerable to Web Cache Poisoning by using a vector called parameter cloaking. When the attacker can separate query parameters using a semicolon (;), they can cause a difference in the interpretation of the request between the proxy (running with default configuration) and the server. This can result in malicious requests being cached as completely safe ones, as the proxy would usually not see the semicolon as a separator, and therefore would not include it in a cache key of an unkeyed parameter.

PoC

GET /?q=legitimate&utm_content=1;q=malicious HTTP/1.1

Host: somesite.com

Upgrade-Insecure-Requests: 1

User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.83 Safari/537.36

Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,imag e/webp,image/apng,/;q=0.8,application/signed-exchange;v=b3;q=0.9 Accept-Encoding: gzip, deflate

Accept-Language: en-US,en;q=0.9 Connection: close

The server sees 3 parameters here: q, utm_content and then q again. On the other hand, the proxy considers this full string: 1;q=malicious as the value of utm_content, which is why the cache key would only contain somesite.com/?q=legitimate.

CVSS Scores

version 3.1