Rancher Cross-site Scripting

A Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in Rancher allows remote attackers to execute JavaScript via malicious links. This issue affects: SUSE Rancher Rancher versions prior to 2.5.6. (2021-03-05, CVE-2021-25313)

Rancher 2 through 2.2.4 is vulnerable to a Cross-Site Websocket Hijacking attack that allows an exploiter to gain access to clusters managed by Rancher. The attack requires a victim to be logged into a Rancher server, and then to access a third-party site hosted by the exploiter. Once that is accomplished, the exploiter is able to execute commands against the cluster's Kubernetes API with the permissions and identity of the victim. (2019-09-04, CVE-2019-13209)

Cross site scripting is an attack where a web page executes code that is injected by an adversary. It usually appears, when users input is presented. This attack can be used to impersonate a user, take over control of the session, or even steal API keys.

The attack can be executed e.g. when you application injects the request parameter directly into the HTML code of the page returned to the user:

https://server.com/confirmation?message=Transaction+Complete

what results in:

<span>Confirmation: Transaction Complete</span>

In that case the message can be modified to become a valid Javascript code, e.g.:

https://server.com/confirmation?message=<script>dangerous javascript code here</script>

and it will be executed locally by the user's browser with full access to the user's personal application/browser data:

<span>Confirmation: <script>dangerous javascript code here</script></span>