Web Cache Poisoning Affecting bottle package, versions [0,0.12.19)
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Test your applications- Snyk ID SNYK-PYTHON-BOTTLE-1017108
- published 18 Jan 2021
- disclosed 13 Oct 2020
- credit Snyk Security Team
Introduced: 13 Oct 2020
CVE-2020-28473 Open this link in a new tabHow to fix?
Upgrade bottle to version 0.12.19 or higher.
Overview
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: example.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.